 1 'Crafting Natures': Aristotle on Animal Design Mariska Leunissen Washington University in St. Louis  Introduction: fixed forms, flexible natures  For Aristotle, living beings are complex composites of matter and form, where form is to be understoodfunctionally,andnotmerelyasshape,asaspecificcombinationofsoul-capacities that characterizes the kind of living being in question. It is a commonplace in Aristotelian scholarship thatboththeseformsoflivingbeingsandtheenmatteredanimalspeciestowhichtheygiveriseare 'fixed'. Forms are 'fixed' in the sense that they – without being eternal themselves – are replicated eternally throughsexualreproductionfromfathertooffspring:theoffspringreceivesa'potentialfor form' that is formally (but not numerically) identical to the form its father possesses in actuality.1 Sincethispotentialforformisforthemostpart–thatis,ifnothinggreaterimpedes–realized in thesameway,andsincethecosmosiseternalintime,Aristotlebelievesthatthereisacontinuous generation–andcorruption–oforganismsthatareoneinformandthatinstantiatethesamerange ofanimalspecies.2Withintheseconfines,thereisnoroomforatransformationofspecies. In seeming contradiction with this fixity of species, however, Aristotle's biological works often stress the flexibility of nature during embryogenesis and the later development of animals. Aristotle typically describes the process of the actualization of a potential for form into an actual animal in terms of 'formal natures' 'making' or 'producing' the animal. This formal nature instantiates the animal's efficient, formal, and final cause (which is identical to its soul), and followingthecraft-modelalreadyemployedbyPlato,Aristotlepersonifies this internalprincipleas actingforthesakeofsomething,whilefollowingacertain logosor'guideline'forbuilding(see,e.g., PAI1,641a23-28;DAII1,412a19-21andGAIV4,770b17).3Giventheunchangeabilityofanimal   * This is a revision of a paper presented at the Humboldt University in Berlin, at a meeting of the St. Louis Area PhilosophyofScienceAssociation, andat theCenterforPhilosophicExchangeatSUNYBrockport. Iwould like to thanktheaudienceswithwhomIdiscussedthispaperonthoseoccasions,andespeciallyDevinHenryforhisextensive writtencommentsonanearlierdraft. 1Onthismodelofreproductionas'formalreplication',seeGotthelf(1987);Lennox(2001a),230-232;andWitt(1994b), 222-228.OnthesenseinwhichAristotelianspeciesareeternal,seeCooper(1982)andLennox(2001a),131-159. 2SeeDA II4,415a25-b7;GAII1,731b24-732a1;MetaV28,1024a29-31andVII8;andGCII10-11.Onthefixityof speciesinAristotle,see,e.g.,Cooper(1982),197-222andSorabji(1980),145-6. 3Thesenatures,however,operateas internalprinciples;Aristotledoesnotendorse theexternal,providentialkindof teleologyaspresentedinPlato'sTimaeus.Onthisissue,seeLennox(2001a),182-204and(2009),359-60.  2 species,onewouldexpectthese'guidelines',or'definitionsoftheanimal'ssubstantialbeing,'tobe ratherstrictandprecise,butinsteadAristotlesuggeststhattheyareunderdetermined.Insteadofthis being specified by the animal's logos, Aristotle claims that it is somehow 'up to' formal natures to determinewhichpartstoproducefortheperformanceofacertainfunction,how manyofthoseparts theyshouldmake,andwhereintheanimalbodytheyshouldplacethem.Evidently,eventhoughthe starting points (i.e., the potentials for form) andend points (i.e., the fully developed animals of a givenspecies)ofanimalgenerationare'fixed'and'permanent'featuresoftheworld,theindividual actions of the formal natures through which this process is carried out are not similarly predetermined. My purposes in this paper are, first, to delineate the range of flexibility Aristotle believes naturesactuallyhave intheirdesignofanimals,andsecond, todrawoutsomeofthe implications this has for our understanding of Aristotle's account of embryology and his theory of natural teleology. I will argue that Aristotle's tendency to think of the activities of formal natures in the productionofanimalsas ifperformedbytinkeringcraftsmenshowsthatforhim,thestructureand functionalityanimalshaveisasmucharesultoftheteleologyembeddedintheirformsasitisofthe goal-directedactionsperformedbytheirformalnatureinrealizingthoseforms.Thisindicatesthatat leastat the level of embryogenesis, Aristotle does allow for something like a transformationof species4 andthathisviewofdevelopmentisepigeneticinthetruesenseoftheterm.Thatis,the'guidelines' forbuildingwithwhichnatureworksdonotpredetermineinadvanceallthechangesthatneedtobe made, but rather leave room for nature to make adjustments to animal design 'on the fly,' as the developmentproceeds.Forhistheoryofnaturalteleologythismeansthattheunderlyingphysiology must be rather complex and flexible: the potentials for form that guide the realization of those speciesaredynamic,ratherthanblind,automatedself-regulatingprinciples,astheyareshowntobe capableofrespondingto'unexpected'changesincircumstances.5  . The problem of animal design in Aristotle's biology  InhisfamousexhortationtothestudyofphilosophyintheParts of Animals,Aristotlearguesthatwe should not look down on the study of animals that are not pleasing to perception, because 'the   4FortheideathatAristotle'sunderstandingofnaturalkindsisnotassuch'anti-evolutionary',seealreadyBalme(1972), 97-98;Granger(1987),110-116;Henry(2006),451-455;andLennox(2001a),160-162. 5MypaperthusprovidesfurtherevidenceforAllanGotthelf'ssuggestionsonhowtocashoutAristotle'suseofcraftlanguageinnon-intentional,physiologicalterms:seeGotthelf(1987)andLeunissen&Gotthelf(2010),342.  3 naturethatcraftedthem(ἡδημιουργήσασαφύσις)likewiseprovidesextraordinarypleasurestothose whoareabletoknowtheircausesandarebynaturephilosophers(PAI5,645a7-10).'Hecontinues bysayingthatitwouldbeunreasonableandabsurdthat,'ifweenjoystudyinglikenessesofanimals onthegroundthatweareatthesametimestudyingtheartthatcraftedthem,suchaspaintingor sculpture, we would not be even more fond of the study of things constituted bynature, at least when we can observe their causes (645a11-15).' Aristotle's point here is that it helps to think of animalsasbeingnolesstheresultofakindofcraftsmanshipasaretheirlikenessesinpaintorstone, and that therefore the study of their causes should provide similar pleasures to those who are philosophicallyminded. This depiction of nature as a craftsman is, as I indicated in the introduction, common in Aristotle's biological works, and it often merely serves thepurpose of elucidating obscure organic processes,suchasembryogenesisintheGeneration of Animals.ForAristotle,theprocessesofartificial productionandnaturalgenerationaresimilarinthattheybothinvolvereplicationsofforminmatter through the operation of an efficient cause, and both take place for the sake of creating an organized, functioning whole.6 Also, in both processes, the efficient cause starts out as operating fromtheoutside,butinnaturalgenerationitultimatelybecomesinternaltothegenerativeprocessas theanimal'ssoul.Thus,whenexplainingwhyembryogenesisandbirthmusttakeplaceinthefemale, Aristotlelikensthemalesementoacarpenterandapotter,whomustkeepinclosecontacttotheir respectivematerials,andtoanarchitect,whois'inthebuildingitmakes'(GAI22,730a32-b8).In those male animals that do not emit semen, 'nature resembles those who model clay rather than carpenters',becauseitdoesnotshapethematerialwithtools,butwithitsownhands(730b8-32;cf. PAII9,654b27-32).Oncetheheartispresent,theremainingformationoftheembryotakesplace through the actions ofthe soul, which makes useof heat and cold as its tools (GAII 1, 734b20735a29;II4,740b25-741a4;andII6,743a36-b5)andproceedsinamannerresemblingpainters(GA II6,743b18-25):  Theupperhalfof thebody, then, isfirstmarkedout intheorderofdevelopment;as time goes on the lower also reaches its full size in the blooded animals. All the parts are first markedoutintheiroutlinesandacquirelaterontheircolorandsoftnessorhardness,exactly as if nature were a painter producing a work of art (ἀτεχνῶς ὥσπερ ἂν ὑπὸ ζωγράφου τῆς   6SeeBroadie(1990)andLennox(2001a),230-232.  4 φύσεως δημιουργούμενα), for painters, too, first sketch in (ὑπογράψαντες) the animal with linesandonlyafterthatputinthecolors.7  These comparisonshelp to visualize the processof reproduction, and are compatible with a nonintentionalmodelofteleology.AtleastwithinthecontextoftheGeneration of Animals,weneversee thesenaturalefficientcauseswaverordeliberateabouthowbesttoproduceananimaloritsparts. Just as expert craftsmen, formal natures automatically 'know' what to do and in what order to performeachoftheiractions(cf.GAI23,731a25andtheanalogyofnaturetoagoodhousekeeper inII6,744b11-27).8  However,notallofAristotle'sdepictionsofnaturesascraftsmenareas innocentas these. Especially in the Parts of Animals, Aristotle drops the comparisons and turns nature itself into a craftsmanwhomakeschoices,takesawayoraddsparts,andwishestodothings.Itisherethatwe findtheanimaldesigntobeinpart'upto'nature,ratherthanbeingcompletelydeterminedbythe animal's substantial being. The purpose of this imagery, I submit, is no longer didactic, but explanatory:whentryingtoexplainwhycertainpartsortheirdifferentiationsbelongtothekindsof animalstheydo,thinkingaboutformalnaturesastinkeringcraftsmen–oftenembeddedintheform of teleological principles such as 'nature does nothing in vain' – becomes an important heuristic strategyforAristotleforthediscoveryofcauses.Whereothermethodsfailtorevealthecauseofthe presence,absence,ordifferentiationofapart,Aristotleappealstoahypotheticalmomentintimeat whichanaturefirstdesignedtheanimal(inamannerresemblingthe'firstcreation'ofhumanbeings in Plato'sTimaeus).9 By comparing the features an animal 'should' have had, given its substantial being, to the features the animal in fact can be observed to have, Aristotle discovers a design problem and then explains the animal's actual features as nature's teleological solution to that problem.TheimagesofcraftingnaturesasusedintheParts of Animals arethusremnantsofthought experiments (that combine forms of reasoning very similar to adaptive thinking and reverse engineering)Aristotleengagedinwhileattemptingtofindexplanationsofanomaliesinanimals,but theyalsoadda levelofcomplexityandflexibility tohistheoryofnatural teleology:noteverything   7SometimesAristotledepictstheactionsofnatureitselfasthoseofapainter:e.g.,nature'sketchedin'(ὑπέγραψεν)two blood-vesselsrunningfromtheheartoftheembryo(GAII4,740a28-9),skeletalanaloguesinsepiaandsquids(PA II8, 654a24-6),andhaironhumanchests(PA II14,658a21-3),andit'decorated'(ἐπικεκόσμηκεν)longtailswithhair(PA II 14,658a31-5).Cf.Aristotle'scomparisonofblood-vesselstoaframe-work(ὡςπερὶὑπογραφὴν)inGA IV1,764b30. 8Cf.Broadie(1990),396-398. 9Cf.Gotthelf(1987),184n.46onnatures 'deciding'howmanystomachsandsetsofteethtogiveacertainanimal: 'It wouldnotbeamisstoseeavaguedevelopmentalhypothesisinthebackground.'  5 that is good in the world of natural phenomena derives from an in itself not further explicable, predeterminedgoodembeddedinforms. In the remainder, I provide support forthese claimsby discussing three kinds of cases in whichAristotledescribesformalnaturesasdeviatingfromthe'originaldesign'orthe'instructions' intheanimal'sform,consistingin(1)theremovalofparts;(2)there-useofalreadyexistingpartsfor asecondfunction;and(3) theproductionof 'luxury'features(suchashairs,horns,andeyebrows) frommateriallynecessitatedresidues.Usingthesecasesasastartingpoint,Iwillthen,insections2 and3, layouttheparametersfortheactionsofformalnatures, first theonesthatarequalified as being'necessary'forit,andthentheactionsthatarequalifiedas'best'oras'forthebetter'.10 Case 1: removing parts  The clearest case in which Aristotle claims formalnatures deviate from theoriginal animal design pertainsto'paradoxical'absencesofparts.Theabsenceofapartisparadoxicalwhenonehasreason toexpectthatparttobepresentintheanimalinquestiononthegroundsthatitcanbeobservedto be present in either all the members of the animal's wider kind, or in many or all closely related animals(forinstance,fish–whichareswimmersbydefinition–allhavefins,butserpentinefishdo not; monkeys have tails, but humans – who are in many respects similar to these blooded landdwellers – do not). Only if the part belongs (or reasonably could be expected to belong) to the animal's original design, Aristotle tries to explain its absence, and he does so by appealing to the teleologicalprinciplethat'naturedoesnothinginvain,butalwaysfromamongthepossibilitiesdoes what is best for each being'.11 The principle is an empirical hypothesis about the goal-directed actionsofformalnaturesinthegenerationofanimals:seeingthatforthemostpartanimalsarenot equipped with useless or non-functioningparts, we may infer that this applies to all the works of natureandpositthatnaturenever producesanythinginvain(seeIA2,704b12-15).12Suchageneral ruleofnaturethenhelpstogenerateathoughtexperiment:imaginethemissingparttobepresent, and'see'ifyoucandetectsomeotherfeatureoftheanimalthatwouldinterferewithitsfunctionality orthatwouldmakeitspresenceredundant.Ifthereisnosuchinterferingpart,thenowmissingpart   10SomeoftheexamplesarediscussedmorefullyinLeunissen(2010);hereIreexaminethemwithafocusonAristotle's viewsonanimaldesign. 11Onthescientificstatusanduseofteleologicalprinciples,seeLennox(2001a),182-204andLeunissen(2010),112-151. 12 This does not mean that according to Aristotleeverything in nature must be present for a purpose (seePA IV2 677a15-18), but rather that formal natures cannot perform non-purposeful actions, such as placing horns on bulls' shoulders(PAIII2,663a34-b13);cf.alsoPA II8,653b27-9andII9,654b23-4.  6 mustbeabsentfornon-teleologicalreasons:itmustbeduetoalackofconstitutivematerialsinthat animal,whichisamaterialconstraint.13Ifthereissuchaninterferingpart,however,itmustbethe cause for why the now missing part is in fact absent: the animal's formal nature 'decided' not to produce(oreven:totakeaway)thatpartonthegroundsthatitspresencewouldhavebeeninvain inthisparticularkindofanimal. Letmequoteoneofmyfavoriteexamples(IA 8,708a9-20):14  Insnakesthecauseofwhytheyarefootlessis,both,thatnaturedoesnothinginvain,but alwaysfromamongthepossibilities,[does]whatisbestforeachthing,preservingtheproper substantial being of each and its essence; and, in addition, that which we stated before, namely that no blooded animal can move itself at more than four points. For from these [twoprinciples]itisevidentthatofthebloodedanimalswhoselengthisoutofproportionto therestofthenatureoftheirbody,likesnakes,noneofthempossiblycanhavelimbs.For theycannothavemorethanfourfeet(sinceinthatcasetheywouldbebloodless),andif they had two feet or four they would be almost completely immobile: so slow and useless would their movementnecessarilybe.  Observationshowsthatallbloodedanimalsthatliveonlandhavefourfeet:theysharetoacertain extent the same form, and their design can therefore be expected to share certain co-extensive featureslikethepossessionofamaximumoffourfeet.Thesnake,however,possessesallthetypical properties thatbelongtoblooded land-dwellers,exceptforfeet.Aristotleexplainsthisabsenceby pointingoutthatthepresenceoffourfeetinsnakeswould have beeninvain,onaccountofthesnake's disproportionatedimensions(andgivingmorethanfourfeetisimpossible,asthiswouldviolatethe substantialbeingofbloodedanimals).Aquickthoughtexperimentreveals thatnobloodedanimal whoselengthisoutofproportiontotherestoftheirbodywouldbeabletomoveswiftlywitheither twoorfourfeet,andinordertoremedythatdesignproblem,nature'decided'nottoproducefeetin   13 On cases where the actions of formal natures are compromised or restricted by the animal's material nature, see Lennox (2001a),182-204and (2001b),228;onanimals lackingpartsdue toa 'deformationof theirkind',whichgoes backtoamaterialdistortionduringembryogenesis(cf.HAVIII2,589b29-590a11),seeGranger(1987),110-16. 14Forotherexamples,seePA II13,658a6-10;IV11,690b14-18;IV12,694a16-18;IV13,696a10-15;IA2,704b12-18; 4,705b25-29;Resp.10,476a11-15;andGAV1,781b22-8.  7 suchanimals.Withthisinformation,itwouldthenbepossibletoformulateascientificexplanation thatdoesnotappealtoanyconsciousintentionalityinnature.15  Inafewcases,Aristotleevensuggeststhatformalnaturesactively'takeaway'featuresinthe production of animals, again because their presence would be in vain. This is, for instance, how Aristotle explains the absence of sideways jaw motions in fish, birds, and egg-laying four-footed animals(PAIV11,691a27-b4):  Sincetheheadisdividedintwo,theupperpartandthelower,mankindandthelive-bearing, four-footed animals move their jaws up, down, and sideways, while fish, birds, and egglaying four-footed animals only move them up and down. That is because up-and-down movementisusefulforbitingandcutting,whilesidewaysmovementisusefulforgrinding. Thereforeforthosethathavegrindingteeth,sidewaysmotionisuseful,butforthosethatdo not,itisnotusefulatall,which is why it is taken away (ἀφῄρηται)from all such animals;fornature producesnothingsuperfluous.  Apparently, the 'proto-typical' way in which jaws are produced in animals (for the sake of aiding nutrition) allows them to move up and down as well as sideways. However, in those that lack grinding teeth, the sideways motion would be in vain (just imagine its presence!), which is why naturetakesitaway(cf.PAIV10,689b21-5;CaelII8,290a29-35;HAII17,508a8-11;andPl.Ti 33d-34a).  In both examples, the absence of a part is explained as an improvement of the design impliedbytheanimal'sform:blindlyfollowingthe instructions inthedefinitionofthesubstantial beingwouldleadtoanimalswithimproperlyfunctioningorvainparts,butfortunately,'naturedoes nothinginvain'.  Case 2: reusing parts A second case in which Aristotle claims formal natures make adjustments to the original animal design involves the 'reuse' of an already existing part for a second function. Typically, natures   15UsingtheformatofthePosterior Analytics, theexplanationwouldrunasfollows:premise1:having(amaximumof) fourfeetholdsofnobloodedanimalwhoselengthisoutofproportiontotherestofitsbody;premise2:havingthe lengthoutofproportiontotherestoftheirbodyholdsofallsnakes(whicharebloodedanimals);conclusion:having(a maximumof)fourfeetholdsofnosnakes.  8 produceone(setof)part(s)forthesakeofrealizingeachofthefunctionsthatarespecifiedbythe definitionofthesubstantialbeing(Ireturntothis'rule'belowinsection3),andeachfunctionhas itsownproperrealizingpart.Forinstance,iftheanimalistobeaflyer, itreceiveswings(andnot someotherpart),becausewingsarethenecessaryprerequisitesfortherealizationofthefunctionof flying, and so natures produce wings in all birds (PA IV 12, 693b6-14), even if not all birds ever engage in flight (693b28-694a9). In a few cases, however, Aristotle believes that the function specified by the animal's form cannot be realized in the usual way: its proper part cannot be producedatallorcannotbeproducedinawaythatmakesitsuitableforthefunctioninquestion, andnatureswillhavetoimproviseandmakeuseofsomeotherpartthatisalreadyavailableinthe animaltomaketheperformanceofthatfunctionpossible.Aristotleemphasizesthatthepartsthat arebeing'reused'bynaturedidnotcometobeforthesakeofthatsecondfunction:instead,they came to be for the sake of performing some other function (which is their primary and proper function), but since they are present and possess the right kind of material potentials, nature can easilyadoptormodifythemforthesakeofallowingthemtoperformasecondfunction.Aristotle describestheactionsofnatureinthesecasesasmakinguseofapartforanotheruse,wheretheverb forusingbearsconnotationsofmisuseoradditionaluse(cf.Cael. I3,270b24).16 Aniceexampleofsuchareusedpartistheelephant'strunk.17Inalongpassage(PAII16, 658b32-659a36),Aristotlefirstexplainswhyelephantshavethespecificnosetheyhave.Elephants havea nose in virtueof being abreatherof air (that is, noses are anecessaryprerequisite forthe performance of the necessary function of cooling), but they have the specific, long nose they have becausetheyneedanorganforbreathingairwhilebeinginthewaterlookingfornourishment:long nosesfunctionforelephants likesnorkelsdoforhumandivers(659a6-12).However, inorderfor trunkstobesolong,theyhavetobe–ofconditionalnecessity–softandflexible,andAristotlegoes ontoexplainhownaturemakesuseofthesematerialpotentialsofthetrunkinordertomake upfor theuselessnessoftheirfeetforgraspingfood(659a20-30;34-6):  Since[thetrunk]issuch[i.e.,softandflexible],nature,as itisusedto,usesthesameparts forseveralthings(ἡφύσιςπαρακαταχρῆται,καθάπερεἴωθεν,ἐπὶπλείονατοῖςαὐτοῖςμορίοις), [hereusing]itinplaceoftheuseoffrontfeet.Forfour-footedanimalswithmanytoeshave front feet in place of hands, not merely for the sake of supporting their weight. And the   16TheGreekis(παρα)καταχρῆται;seePAII16,659b34-660a2;III9,671a35-b2;IV 10,688a19-25,689a5-7,689b34690a4;andResp. 7,473a23-5. 17SeeGotthelf(1997a).  9 elephants are members of this group; that is, they have feet that are neither cloven- nor solid-hoofed.Butsincethesizeandweightoftheirbodyaregreat,theirfeetareonlyforthe sake of support, and because of their slowness and their natural unsuitability for bending, theyareuselessforanythingelse...Andtheuseofitsfeethavingbeentakenaway,nature,as wesaid,alsomakesuseofthispartfor the service that would have been provided by the feet.  Typically,four-footedanimalswithmanytoeshavefeetthatarecapableofprovidingbothsupport fortheirbodiesandmeanstotransportfoodtotheirmouths: theform'many-toedfour-footer' is 'normally' realized by giving these animals four supporting, but bendable feet. However, in elephants,thisuseoffeetistakenaway,andsotheirnatureshavetodeviatefromtheoriginaldesign by assigning a second function to the elephant's trunk, but without having to change any of its features.Althoughphysically,thedesignoftheelephanthasnotchanged,natureshadtomovethe functionofgraspingfoodtothetrunk,afunctionwhichwas'supposedtobe'performedbyitsfeet. In cases like this, nature still realizes all the functions specified by the definition of the substantialbeingoftheanimal,but,becauseofthedesign-problemsthatonlybecomeclearduring theanimal'sproductionprocess,ithastodosoinan'unexpected'way.18 Case 3: adding 'bonus features'  A third case in which formal natures adjust an animal's original design involves the use of extra materialsforwhichthereare,sotospeak,noinstructionsinthedefinitionofthesubstantialbeingof theanimal.Theteleologicalprocessesinvolvedintherealizationoftheanimal'spotentialforform sometimes produce – accidentally and of material necessity – flows of residues or even entire structures. And even though these materials or structures are thus not themselves an immediate product of the operationofteleology(their coming tobe is not conditionally necessitated for the sake of realizing functions specified by the animal's form), formal natures can use them 'for the better' by turning them into parts that increase the well-being of the animal, instead of just discardingthemfromthebody.Onceco-optedbytheformalnatures,thesepartsbecomebeneficial   18 There is a slightly different (and unique) case where Aristotle suggests that nature remedies a problem with the positioningofonepartbyconstructinganother:becauseofothernecessitatingfactors,naturehastoplacethewindpipe infrontoftheesophagus,where 'itis interferedwithbythefood'(PAIII3,664b20-1).So, inordertopreventfood fromslippingdownthewindpipe,nature'hasconstructedtheepiglottis'(664b21-22),to'remedy(ἰάτρευκεν)thebadness ofthepositionofthewindpipe'(665a7-8).  10 'bonusfeatures'addedtotheanimal'soriginaldesign:hypotheticallyspeaking,theanimalcouldhave donewithoutthem,butwiththeirpresence,itisbetteroff.19 Eyebrowsandeyelashesaresuch'added'features(PAII15,658b14-25):  Theeyebrowsandeyelashesarebothforprotection...Theeyelidsareat theendsofsmall bloodvessels;forwheretheskinterminates,thesmallbloodvesselsalsoreachtheirlimit.So becausethemoistsecretionsoozingarebodily,itisnecessarythat–unlesssomefunctionof naturestops itwithaviewtoanotheruse(ἂνμήτιτῆςφύσεωςἔργονἐμποδίσῃπρὸςἄλλην χρῆσιν) – even owing to a cause such as this, hair from necessity comes to be in these locations.  As Aristotle indicates, the structures that form eyebrows and eyelashes come to be of material necessity–aprocessthatisnotinitiatedbyaformalnature,butalsonot stoppedbyit.Natureallows thegrowthofeyebrowsandeyelashes,becauseoncepresent,thesestructures–becauseoftheirhard andearthennatureandbecauseofthelocationwheretheyofnecessityappear–servethefunction ofprotection. Inothercases,naturedoesstoptheflowofmaterial,butonlytoredirectittootherpartsin thebody,whereitusesitfortheproductionofbeneficialparts(PA III2663b22-35):  Butwemustsaywhatthecharacterofthenecessarynatureis,and,hownatureaccordingto the accountmakes use of things presentofnecessity forthe sake of something... For the residualsurplusofthissortof[earthen]body,beingpresent inthe largeroftheanimals, is used by nature for protection and advantage (ἐπὶ βοήθειαν καὶ τὸ συμφέρον καταχρῆται ἡ φύσις), and the surplus, which flows of necessity to the upper region, in some cases it distributes(ἀπένειμε)toteethandtusks,inothercasestohorns.  Boththecarefulteleologicallanguageintheseexamples('for'insteadofthemoretechnical'forthe sake of') and the reference to material necessity in the coming to be of these features are typical characteristics of the 'bonus features' in Aristotle's biology. They are never the necessary prerequisites for the performance of necessary functions as specified by the definition of the   19 I call this causal process of naturesmaking use of materials that have come to be of material necessity 'secondary teleology', using 'primary teleology' for the realization of a potential for form through stages shaped by conditional necessity(conformGotthelf's1987interpretationofteleology):seeLeunissen(2010).  11 substantialbeingoftheanimal.Instead,theyassistotherpartsinperformingtheirfunctions,suchas kidneyshelpingthebladdertocollectresidue(PA III7,670b23-7),orperformfunctionsthatappear tobenon-necessaryfortheanimaltoreproduceorsurvive,suchashornsprovidingprotectionto themaledeerthathavethem(PA III1,661b28-662a2).Theirfunctionsarethereforesubsidiaryor luxury,andthepartsthemselvesareoftensimplyreferredtoasbeing'forthebetter'. Theavailabilityofmateriallynecessitatedresiduesorstructures inthesecasesthusprovide 'extra'possibilitiesfornaturestoproducefeaturesthatincreasetheanimal'swellbeingandthereby improvethem,eventhoughnoneofthesefeatureswerepartoftheoriginaldesign.  Insum,thedevelopmentofananimalconsistsforAristotleintheactualizationofaninternal,preexisting potential for form, transmitted by the father into the female menses and brought to completionthroughtheanimal'sformalnature.Itisthispotentialforformthatencodestheanimal's development,andthatguides–but not completely predetermines–theactionsoftheformalnatureduring thedifferentstagesofanimaldevelopment.Thepictureoftheactionsofformalnaturesthatarises from the three cases discussed above is that formal natures always act in accordance with the specificationsinthedefinitionofthesubstantialbeingoftheanimaltheyareproducing,unless during the production process this turns out not to be beneficial or possible, and that they improve the designofananimalif this is possible duetotheavailabilityofextramaterials.Inthesectionsbelow,I furtherspecifytheparametersfortheactionsoftheformalnaturewithinwhichthese 'epigenetic' adjustmentstakeplace.  2. Constraints on formal natures: doing the necessary  WhenAristotlequalifiesanactionasbeingnecessaryforaformalnaturetoperform,thattypically meansthattheactionisnecessarygiven thesubstantialbeingoftheanimalthatisbeingbroughtinto being.Withouttherealizationofthefunctionsandotherfeaturesthatarespecifiedinthedefinition ofthesubstantialbeingoftheanimal,theanimalinquestioncannotexistorbethekindofanimalit is.Formalnaturesthereforehave toproducethenecessaryprerequisitesforanimalstosurviveandto havetheidentitytheyhave(cf.PA I1,640a33-35);itispartoftheteleologyofnaturethatformal naturesneverfallshortinproducingthosenecessities(seeDAIII9,432b21-6). Unfortunately, Aristotle is not very explicit about what kinds and how many of those functions and features exactly are included in thedefinition of an animal's substantial being. At a  12 minimum,ashasalreadybeensuggestedbyGotthelfandCode,20thesespecificationsinclude(1)the vital and essential soul functions as specified by the relevant differentiae21 of the animal, and sometimesspecificorganicpartsthemselves;22(2)thesizesanddimensionsofanimals;23and(3)the bloodednessorbloodlessnessofananimal.24Itisplausiblethatthedefinitionalsospecifies(4)the ratio of the elemental blend constitutive of the animal's material nature. Below, I discuss the implicationsthesefourkindsofspecificationshavefortheactionsoftheformalnatures,indicating both what actions are necessary for them to perform and (less so) what actions are impossible. Together,theseconstraintsontheactionsoftheformalnaturesexhibitthelevelofpredeterminism in Aristotle's embryology and the extent to which teleology is already embedded in the forms of animals.  Thefirstcategoryoffeatures listed inthedefinitionofthesubstantialbeingoftheanimal,that is, the vital and essential functions to be performed by the animal in question, provides stringent guidelines for whatparts formal naturesmust make. Inorder to realize the animal's form, formal naturesmustproduce(a)thosepartsthatareexplicitlymentionedinthedefinitionofthesubstantial being as well as (b) the parts that are the necessary prerequisites for the realization of the vital and essential functions as specified by the relevant differentiae in that definition. For instance, the definitionofhumanbeingswillinclude'is lunged'and'isabletosee',whichmeansthattheymust have lungsandeyes, theproperpartsfortherealizationofvision(GA V1,778a29-b19).Natures cannotproducehumanswithouteitheroftheseparts,becauseinthatcasehumanswouldimmediately failtoreachtheirnaturalends(cf.GAIV4,771a11-14). In order for us to reconstruct whether a part is such a necessary prerequisite, Aristotle suggestswelookatitsdistributionamonganimalsthatallperformthefunctionassociatedwiththat part:observationshowsthattheremaywellbeseveralpartsassociatedwiththeperformanceofthe samefunction,butonlythepartthatispresentin all animalsthatperformitisnecessary;theother partsmustbesubsidiary.For instance,ductsforsemenandtestesbothplayarole inmalesexual reproduction,butwhereasductsforsemenarepresentinallmalesthatreproducesexually,testesare not(GAI4,717a11-31):   20Code(1997),139-140andGotthelf(1985),27-54;(1987),190-191. 21PAII8,653b19-23(cf.II2,647a20-3);IV12,693b2-13;andIV13,695b17-25. 22PAIII6,669b8-12andIV8,684a32-b1. 23PAIV9,685b12-15(cf.IA 8,708a9-20);PA IV6,683a18-19;IA8,708a9-20;GA II6,745a5-6;DAII4,416a15-18; andPolV9,1309b18-35. 24PAIV5,678a31-5;IV12,693b2-13;andIV13,695b17-26.  13  Nowifnaturedoeseverythingeitherbecauseitisnecessary,orbecauseitisbetter(εἰδὴπᾶν ἡφύσιςἢδιὰτὸἀναγκαῖονποιεῖἢδιὰτὸβέλτιον),thispart[i.e.,testes],too,mustbebecause ofoneortheother.Thatitisnotnecessaryforgenerationisevident:foritwouldbepresent inallthatgenerate,butasitisneitherthesnakenorthefishhavetestes(fortheyhavebeen seen coupling and with the channels full of semen). It remains then that they are for the better in some way... Those who need to be more temperate have in the one case [of nutriment]intestinesthatarenotstraight,andintheothercase[ofsexualreproduction]their ducts twisted to prevent their desire being too violent and hasty. The testes are built (μεμηχανημένοι)forthis;fortheymakethemovementofthespermaticsecretionsteadier...  Bypostulatingthat theactionsofformalnaturesareeithernecessaryorforthebetter,Aristotle is abletoreconstruct thestatusofapartaseithera necessaryprerequisitefortheperformanceofa necessaryfunction(here:ductsarethenecessaryprerequisitesformalesexualreproduction),orasa subsidiarypartthathelpstheperformanceofthatfunctioninasubgroupofanimals(here:testesare forslowingdownreproductioninmalesthataretoopassionate). This requirement for nature toproduce thenecessary parts is onlyoverruled inthose rare caseswhere,aswesawabove,thepresenceofthetypicalnecessarypartinacertainkindofanimal would be in vain: in those cases, nature has to come up with an alternative solution to allow the animaltoperformitsvitalandessentialfunctions.  The animal's basic size and dimensions constitute the second categoryof features specified inthe definitionofitssubstantialbeing.Naturecannottinkerwiththem(althoughenvironmentalfactors may cause – relatively small – differences of the more and the less: seeHA VIII 28), even if changing the size or the dimensions would help to solve design problems. For instance, shorter snakeswouldhavebeenabletowalkwellwithfourfeet,andsmaller(andhencelighter)elephants would not have needed such sturdy feet, thus enabling them to use their feet for grasping food. However,inbothcases,Aristotletakestheanimal'ssizeasacausallybasicfeatureandassomething thatisnotuptoformalnaturestochange.Similarly,observationshowsthatonekindofoctopushas one row of suckers, whereas another has two, but this differentiation has nothing to do with teleology(PAIV9,685b12-16):   14 Nowwhiletheotheroctopuseshavetworowsofsuckers,onekindofoctopushasasingle row.This isbecauseofthe lengthandthinnessoftheirnature;for it isnecessarythat the narrowtentacleshouldhaveasinglerowofsuckers.It isnot, then,because it isbest that theyhavethisfeature,butbecause it isnecessaryowingtothedistinctiveaccountoftheir substantial being (οὐκ οὖν ὡς βέλτιστον ἔχουσιν, ἀλλ' ὡς ἀναγκαῖον διὰ τὸν ἴδιον λόγον τῆς οὐσίας).  Aristotlesuggeststhat,instead,thedifferentiationisa necessary consequence ofthedifferencesinsizeof the two kinds of octopus. Changing the size or the dimensions of an animal will destroy its functionalityorturnitintoanaltogetherdifferentkindofbeing(cf.PolV3,1302b33-1303a2;V9, 1309b18-35; and VII 4, 1326a35-b2), and is thereforenot a possible action for formal natures to perform.  Thethirdcategoryoffeaturesspecifiedinthedefinitionofthesubstantialbeingofanimalsistheir having(red)bloodorbeingbloodless(that is,havingananalogueofblood).This isan important specification(andoneofthemost importantdifferentiaofanimals:HAI6,490b7-32),because it does not only entail the necessity of nature producing blood or its analogue in the animal in question,butalsothenecessityofproducingcertainothersetsofparts. For instance,sincebloodformsthematterandnourishmentforthewholebody(see,e.g., PAII3,650b6-7;II6,652a6-7;andIII5,668a5-13),everybloodedanimalmusthavepartsforthe productionofbloodandforitsdistribution.Thismeans,amongothers,thattheformalnaturesof bloodedanimalshave toproduceaheart(PAII1,647a35-b8andIII4,665b10-15),bloodvessels (PA III5),andaliver(PA IV2,677a36-b5):'Foritisreasonablethat,sincethenatureoftheliveris vitalandnecessarytoall thebloodedanimals, itsbeingofacertaincharacter isacauseof livinga shorterorlongertime....andnoneoftheothervisceraisnecessarytotheseanimals,butonlythe liver.'Togetherwiththeheart,whichistheoriginofblood,thepresenceoftheliverissobasicto thelifeandsurvivalofbloodedanimalsthatnobloodedanimalcanlivewithoutit;thepresenceof theheartandtheliverisrequiredinallbloodedanimals(cf.PAIII4,665a28-30,665b10,666a24-25 andIII7,670a23-8).Theothervisceralparts,suchasthekidneysandthespleen,arenotinthesame waynecessaryforallbloodedanimals(see,e.g.,PA III7,670b23-7:'thekidneysarepresentinthose thathavethemnot of necessity,butfor the sake of the good and doing well),andarethereforenotpresentin  15 all blooded animals (cf. PA III 9, 671a26-30 and III 12, 673b12-14). The bloodless animals, of course,havenoviscera,butonlyananalogueoftheheart(PA IV5,678a26-b3).  Furthermore, the blooded- or bloodlessness of an animal also puts restrictions on the amount of appendages formal natures can attach to it. Aristotle believes that being blooded correlates universally with (and possibly causes: see IA 6, 707a6-21) having a maximum of four pointsofmotion,andhenceofhavingamaximumoffourappendagesorlocomotiveparts(HAI5, 490a26-b1).Formalnaturesthereforecannotgivemorethanfourappendagestobloodedanimals, even if that would solve problems in their design (see again IA 8, 708a9-20, quoted above). For bloodlessanimalsthereisnosuchrestriction:theycanreceivefourormoreappendages,aslongas thetotalnumberremainseven(IA 8,708a21-b17;cf.PAIV6,682a35-b4).  Afinalfeaturethatislikelyspecifiedbythedefinitionofananimal'ssubstantialbeingistheratio– or,'recipe'–foritsmaterialmake-up,whichdeterminestheproportionofthematerialelementsthat are to be used in the production and constitution of the animal in question (cf.PA I 1, 642a22: λόγοντῆςμίξεως).25Justasthereisaspecificratioofthemixtureforeachofthebodyparts(DA I4, 408a13-18), there is a specific, generic ratio for each kind of animal (and perhaps even for each genderwithinthatkind:cf.GAIV2,767a13-28). Birds,for instance, 'areallconstitutedfromthe samematerial'(PA IV12,694b18),andsincethisisa'given,'formalnatureswilljusthavetomake do with this material in their production of all the subspecies of birds (694b17-20). Similarly, in Aristotle's discussion of the different modes of reproduction in GA II 1, 732a25-733b23, the differences intheelementalmake-upofanimals, incombinationwiththeamountof internalheat they have, are treated as givens, which then cause the differences in perfection in the modes of reproduction(seeespecially732b27-29). However,eventhoughtherecipeforananimal'smaterialnatureisthuslikelydeterminedby its form, the resulting material nature itself can act independently of the form and may pose restrictions on the actions of formal natures. For instance, if an animal lacks the appropriate materialsfortheconstructionofcertainparts, itwill also lacktheparts; if ithasthem,butnot in sufficient amounts, it will lack some of the parts, as formal natures 'cannot (ἀδυνατεῖ) distribute excess materials to multiple locations at the same time' (PA IV 10, 655a28-9).26 Even if formal   25Cf.Gotthelf(1987),192-193. 26 See alsoPA III 2,664a1-3 and IV12, 694a28.Lennox (2001a, 192-3) suggests that natures follow a 'principle of functionalpriority'indecidinghowtousetheavailablematerialsinthesecases.  16 natures'wantto',itisoftenimpossibletocounteractthematerialnatures(seeGAIV10,778a4-9; PAIV5,682a1-8;andPolI5,1254b27-33).  In short, even though Aristotlemakes very little directreference to the 'instructions' contained in the definition of the substantial being of the animal, a good deal of its structural and functional featuresturnouttobepredeterminedbyit.Ontheotherhand,theactionsofformalnaturesarenot exhaustedbydoingwhatisnecessary;theycanalsodowhatispossible,better,orbest.  3. Decisions up to formal natures: doing what is possible, better, or best  Aristotle's depictions of formal natures acting as craftsmen are richest where the instructions providedbythedefinitionsofsubstantialbeingsappeartobeunderdetermined.Inparticular,these instructions turn out to be silent about such questions as howmany parts a formal nature should produce,where in the animal's body they should be placed, and what they should do with extra materials.Inreconstructingthecausesforwhyeachanimalspeciesendsupfunctioningandlooking theway itdoes,Aristotleoften invokesteleologicalprinciples,whichpositcertainrulesofactions formalnatures 'always'or 'never' followwhenproducingtheanimal inquestion.Iwilldiscussthe twomostprominentoftheseteleologicalprinciplesandspecifytheunderlyingdecision-procedures thatAristotleattributestoformalnaturesindesigninganimals. Rule 1: Use extra materials for a purpose, when possible and if this improves the animal  Wealreadyencountered(insection2,above)thefirstteleologicalprinciple,whichassumesthat,asa generalrule,'naturedoeseverythingeitherbecauseitisnecessaryorbecauseitisbetter'.Isuggested that Aristotle uses the principle to identify whether a part is necessary for the performance of a functionthat isspecifiedbytheanimal's substantialbeing,andmust thereforebeproducedbythe formal nature, or whether it is rather subsidiary and therefore not present in all that perform the functioninquestion.Thesecondpartoftheprincipleisofspecialinteresthere,becausethecontrast of subsidiary parts with those that are necessary suggests that the former are optional for formal natures:whereasnecessarypartsaretheresultofactionsnaturesperform'because it isnecessary', subsidiarypartsaretheresultofactionsnaturesperform'becauseitisbetter'.Aristotleoftenrefers totheselatterpartsasbeing'forthebetter',indicating–aswesawinsection1above–thatthese  17 partsarenotconditionallynecessitatedbytheanimal'sform,butareratherduetoformalnatures makinguseofextramaterialsthathavecometobeofmaterialnecessity.  Whetherornotformalnaturesproducesuchsubsidiaryparts,depends,first,onwhetheror not such extra materials are available (and if so, whether they have the appropriate material potentials such that they can be used for improvements of the animal's design), and second, on whetherthefeaturethatcanbemadefromthosematerialsisinfact'forthebetter'fortheanimalin question.Thissecondconditionraisesanimportantquestion:forhowdonatures'know'whatextra featureswillimprovethewell-beingorfunctionalityofananimal?Forinstance,indiscussingtheuse of the 'earthen and warm' residues in birds (PA IV 12, 694a22-b11), Aristotle says that 'in some [nature]constructslengthforthelegs,inothers–insteadofthis–itfillsthegapsintheirfeet.'In bothcases,theusenaturesmakeofidenticalmaterialsisforthebettergiveneachbird'sspecificway of life,buthowdonaturesdeterminethis?Iaddressthisquestionbelow,afterfirstdiscussingthe secondruleofactionforformalnatures, inwhichthe languageofchoiceanddeliberation iseven moreprominent.  Rule 2: always do what is best, given the possibilities  The secondteleological principle assumes that 'nature does nothing in vain, but always, given the possibilities,doeswhat isbestforthesubstantialbeingofeachkindofanimal'.27Insection1,we sawthatAristotleinvokesthefirstpartofthisprinciplefortheexplanationof'paradoxical'absences ofparts.HereIfocusonthesecondpart,whichAristotleinvokestoexplainthepresenceofparts(or theirdifferentiations)incaseswherecomparativeobservationwithwiderorrelatedkindsshowsthat there are several possibilities in which nature could have fulfilled a certain functional need. If we assume,asAristotledoes,thatthisdistributionoffeaturesintheanimalworldisnotrandom,wecan discoveritscausesbythinkingaboutnaturesasdesigner-craftsmen. The thought experiment works as follows: think of the options among which nature can choose as a fixed range, that is, as consisting of the observed range of (the relevantly similar) features realized in actual animals (the hypothetical design space is thus not completely open, but limited to natural possibilities).28 Assuming, then, that natures match each possible part with the animal that is most fitted to use that part, we should investigate the animal's substantial being   27SeeIA2,704b12-18;8,708a9-12;and 12,711a18-29. 28Lennox(2001),214-215.  18 (which,inprinciple,isfixedandcannotbetinkeredwith),andseeifwecanidentifywhataspectofit prompted natures to distribute the parts in the way they did. Take Aristotle's explanation of why humanbeingshavehandsinsteadofforelimbs(PAIV10,687a6-18):  And being upright in nature, humankind has no use for forelimbs, and instead of these, natureprovidesarmsandhands...Itisreasonablethatbecause of their being most intelligent,they receivedhands.Forhandsareinstruments,andnaturealwaysdistributes–likeanintelligent human – each thing to the one who can use it... So if it is better thus, and nature does, amongthepossibilities,whatisbest(ἡδὲφύσιςἐκτῶνἐνδεχομένωνποιεῖτὸβέλτιστον),itis notbecausetheyhavehandsthathumansaremostintelligent,butbecausetheyarethemost intelligentofanimalsthattheyhavehands.  Allbloodedlive-bearingandland-dwellinganimalshaveforelimbs,buthumanshavehands,andthis distributioncannotsimplybeexplainedbyreferencetothe(generic)functionthesepartsperform: both are for grasping. Instead, Aristotle appeals to the teleological actions of formal natures in 'deciding' this distribution: given the twooptions,hands and forelimbs,hands are the best fit for humans,andthereasonwhyliesintheirsubstantialbeing.First,sincehumanswalkupright(thisis anessentialcharacteristic:seePAIV6,686a25-31),theydonotneed–andthereforedonothave– forelimbs for walking. Secondly, and more importantly, since humans are the most intelligent of animals,theyarebestabletousehands,and itbefitsnaturestogivepartstoanimalsthatarebest abletousethem(PA IV10,687a12-16). Aristotlebelievesthatformalnaturesfollowthesameruleofactionwhendecidinghow many partstoproducefortheperformanceoffunctionsaswellasfordecidingwheretoplacethoseparts in the animal body.29 In each case, empirical observation reveals the range of possibilities (of numbersofpartsoroflocationsintheanimalbody)fromwhichnaturesareassumedtochoosethe bestoptionforeachanimal,givenitssubstantialbeing. Inthefirstcase,naturesalwaysassignorgiveasmanypartstoanimalsasarebothnecessary andsufficientforthemtofunction.Ifpossible,animalshaveonepartfortheperformanceofeach function (and never more than one), but if necessary, nature will use the same part for multiple   29Cf.Lennox(2001a),189and203n.16.Naturesevenfollowthisrulefordecidingwhentoproduceparts:seeGAII6, 744a35-b1andGA V8,788b20-789a2.  19 functions.30Forinstance,insectsreceivemanywingsandseparatepartsfordrawinginnourishment and for defense, unless they are too small, in which case they only receive two wings (for this numberissufficientforflying)andonepiercingtongue(PAIV6,683a19-25):  Anditisbetter,wherepossible,nottohavethesameinstrumentfordissimilaruses,butthe onethatisdefensivemostsharp,andtheonethatistobeatonguespongyandabletodraw innourishment.Forwhereitispossiblefortwothingstobeusedfortwofunctionswithout impedingeachother,natureisunaccustomedtomakingthingsasdoesthecoppersmithwho, to economize (πρὸς εὐτέλειαν), makes a spit-and-lampstand; but where this is not possible, naturemakesuseofthesamethingformultiplefunctions.  Aristotle'spointisthatwhileitiscertainlypossiblefornaturesto'cutdown'onthenumberofparts assignedtomany-winged insects, it isnottheircustomtoactfrugally.Ontheotherhand,natures alsodonotassignparts toogenerously.For instance,animalsforwhich it ispossibletoreceivea means of defensive only receive one of these, since that is sufficient (PA III 2, 663a17-18);31 and sincedefenseisanon-necessaryfunction,formalnaturesonlyprovidesuchpartstoanimalsthatare abletousethem–whichismostlytomales(PAIII1,661b28-31). Inthesecondcase,naturesalwaysdistribute orplace partsinabalancedmannerintheanimal's body: parts receive the most valuable location possible, as long as the balance and symmetry between the two halves of the body (along the up and down, left and right, front and back) is preservedandeachparthasacounterpart(cf.PA II7,652a30-3andIV12,695a9-13).Thisruleof balanceddistributionexplains,forinstance,whytheheartislocatedwhereitis(PAIII4,665b1821):'Moreover,itspositionisatanoriginativeplace;foritisnearthemiddle,andmoreabovethan below, and more in front than in the rear; for nature places the more valuable item in the more valuablelocations(ἐντοῖςγὰρτιμιωτέροιςτὸτιμιώτερονκαθίδρυκενἡφύσις),wherenothinggreater prevents it.' The heart is the most important bodily part, which is why it is placed at the most valuable location.32 Functional needs, however, are always given precedence to the value of a location:hence,four-footedanimalsreceivemorehairontheirback,whichiswherethefunctional   30 SeePA II 16, 659a20-2; III1, 661b28-31 and 662a18-24; IV 7, 683b5-7; IV 8, 684a27-30; IV 10, 687a10-15 and 689a4-15;cf.GAI1,716a24-7. 31Cf.Aristotle'sremarkabouttheheartthat'whereverpossible,oneoriginisbetterthanmany'(PAIII4,665b14-15;cf. 665b28-31). 32SeealsoPAIII3,665a23-6;III7,669b18-26and670a4-7;III10,672b19-24;IV11,691a28-b4;GAI8,718b25-9;I 11,719a13-15;II1,732a3-8; IA2,704b18-22;CaelII2,284b10and285a11;andIII4,303b2.  20 need of coverage is highest, whereas humans – whose front and back require equal coverage – receivemorehaironthefront,whichisthemostvaluablelocation(PAII14,658a18-24). Locationsinanimalbodiesderivetheirvaluefromtheirclosenesstotheoriginofthethree mostimportantfunctionsoflivingbeings(cf.IA4,705a31-2:'thisdistinctionisoneoffunction'):33 the front is where the function of sight originates, up is where the function of nourishment originates,andright iswhere locomotionoriginates.34Thesethree locationsandtheircounterparts make up the six dimensions of the body, dividing it up in two parts along three axes. This doublenessofthebody,then,explainswhymanyparts–suchasthesenseorgans–comeinpairs (PAII10,656b27-657a12):  Astothepositionofthesense-organs,alltheorgansofsensehavebeenorderedbynaturein agoodway...Eachofthesenseorgans isdouble onaccountofthebodybeingdouble– onepartontherightandonepartonthe left.Forbecausethebody isdoubleeachofthe organsofsenseisdouble,oneparttheright,theothertheleft...  Note,bytheway,thatthedoublenessofsuchpartsarenoexceptiontothe'economical'workings ofnature:Aristotlebelievesthatthesepartsareoneinform,butdoubleinstructure,andthatthisis infactbest,giventhedoublenessofthebodyitself.35  4. Conclusion: implications for Aristotle's embryology and teleology MyreconstructionaboveofAristotle'sassumptionsabouthownatures'weigh'theavailablenatural possibilitiesandchoosethebestdesignoptionforeachindividualkindofanimalshowshowmany features are not 'preprogrammed' by the definition of the substantial beings of animals. The 'phenotype'ofanimalsdevelopsgradually,asaresultofnaturesnotjustdoingwhatisnecessary,but alsodoingwhat isbetterandbest inresponsetoemergingproblemsandopportunities.However, thisalsobringsusbacktoourpreviousquestions:howdonatures'know'howtodeterminewhatis better or best in those cases, and what do these images of 'crafting natures' mean for Aristotle's theoryofteleology?   33SeeBalme(1987),277andLennox(2001a),266-272. 34SeePAII10,656b22-5;III3,665a13-15;IV7,683b19-24;IA4,705a29-b5and706a21-5; and5,706b12-16. 35Cf.PAIII7,669b36-670a7.Onthedoublenessofthebody,seeLennox(2001a),267-72and(2001b),227.  21 When evaluating Aristotle's craft-imagery of natures, it is important to realize that their abilitytoproducefunctionallivingbeingsonthebasisofformsor'instructions'thatarethemselves underdetermined does not imply that Aristotle believes that these natures deliberate or entertain conscious intentions.Inhisdefenseofnatural teleology,Aristotlearguesthat 'it isabsurdtothink thatnothingcomestobeforthesakeofsomethingunlessthatwhicheffectsthechangeisobserved todeliberate;infact,even art does not deliberate'(PhysII8,199b26-30).Inartificialproduction,thetrue efficientcauseisart,andthusthepsychologicalstatesoftheartistonlymatterinthesensethatart cannot exercise itself, but operates through the artist. Consequently, there is no need to attribute deliberationtonatures,theefficientcausesofnaturalgeneration. Theimagerydoesimply,however,thattheefficiencyofneitherartnornatureliesin'blindly' following predetermined models or forms. For instance, the art of shoemaking does not just compriseproducinglargesetsoflimitedtypesofidenticalshoes,butalsoofmakingadjustmentsto ashoe-moldtoaccommodatethewishesofanespeciallylarge-footedorfashion-sensitiveclientin addition to making good use of the leftover leather materials. Similarly, the 'art' of natures, so to speak, comprises a certain level of creativity or problem-solving ability, which is not dueto some kindofextradeliberatingcapacitythesenaturespossess,butrathertotheirinherent,immanentgoaldirectedness. At the physiological level, that is, when we translate Aristotle's talk of goal-directed natures into realizations of potentials for form in the manner proposed by Gotthelf (see note 5 above), thismeansthatthosepotentialshavetobeequally 'creative'or 'dynamic'.IfIamright in assuming that Aristotle's depictions of natures as craftsmen are no mere metaphors, but in fact reflect different causal patterns that underlie animal generation, thepotentials for formthat guide embryology and the later development of animals cannot be blind, automated self-regulating principles.Rather,theyareflexibleandcomplex,andincludethecapacitiestomakethebestuseof extramaterialsandtorespondtoemergingproblemsorpossibilities. Insum,althoughthinkingaboutformalnaturesas designer-craftsmenprovidesapowerful toolforthediscoveryoftheunderlyingnaturalcauses inanimalgeneration, thisdoesnotcommit Aristotle toademiurgicteleology.Itdoes,however,entail thatwereviseour interpretationofthe causal roles played by the potentials for form in the coming to be of animals: their flexible and dynamicnatureallowsforandinfactdemandsquiteimpressivetransformationsofspecies,ifonlyat thelevelofembryogenesis.    22 References  Balme, D.M. (1987), 'Teleology and Necessity', in A. Gotthelf & J.G. Lennox (eds.),Philosophical Issues in Aristotle's Biology,Cambridge,275-286.  Broadie,S.(1990),'NatureandCraftinAristotelianTeleology',inD.Devereux&P.Pellegrin(eds.), Biologie, Logique et Métaphysique chez Aristote,Paris,389-403.  Code,A.(1997),'ThePriorityofFinalCausesoverEfficientCausesinAristotle'sPartsofAnimals', inW.Kullmann&S.Föllinger(eds.),Aristotelische Biologie: Intentionen, Methoden, Ergebnisse, Stuttgart, 127-143.  Cooper, J.M. (1982), 'Aristotle on Natural Teleology', in M. Schofield & M. Nussbaum (eds.), Language and Logos,Cambridge,197-222.  Gotthelf,A.(1985),'NotestowardsastudyofsubstanceandessenceinAristotle'sParts of Animals II-IV', in A. Gotthelf (ed.),Aristotle on Nature and Living Things: Philosophical and Historical Studies presented to David M. Balme on his Seventieth Birthday, Pittsburgh&Bristol,27-54.  --(1987),'FirstPrinciples inAristotle'sPartsofAnimals',inA.Gotthelf&J.G.Lennox(eds.), Philosophical Issues in Aristotle's Biology,Cambridge,167-198.  --(1997a), 'TheElephant'sNose:FurtherReflectionsontheAxiomaticStructureofBiological Explanations in Aristotle', in W. Kullmann & S. Föllinger (eds.),Aristotelische Biologie: Intentionen, Methoden, Ergebnisse,Stuttgart,85-95.  Granger,H.(1987),'DeformedKindsandtheFixityofSpecies',Classical Quarterly 37,110-116.  Henry,D.(2006),'AristotleontheMechanismofInheritance',Journal of the History of Biology39,425455.  Lennox,J.G.(2001a),Aristotle's Philosophy of Biology, Studies in the Origins of Life Science,Cambridge.  23  --(2001b),Aristotle on the Parts of Animals I-IV, Translated with an Introduction and Commentary by J.G. Lennox,Oxford.  Leunissen,M.(2010),Explanation and Teleology in Aristotle's Science of Nature,Cambridge.  Leunissen,M.&A.Gotthelf(2010),'What'sTeleologygottodowithit?AReinterpretationof Aristotle'sGeneration of AnimalsV',Phronesis 55.4,325-356.  Sorabji,R.(1980),Necessity, Cause, and Blame, Perspectives on Aristotle's Theory,Ithaca.  Witt,C.(1994b),'ThePriorityofActualityinAristotle',inT.Scaltsas,D.Charles,&M.L.Gill(eds.), Unity, Identity, and Explanation in Aristotle's Metaphysics,Oxford,215-228.   Filename: 'Craftingnatures',AristotleonAnimalDesign(Nov.14,2010) Directory: C:\MyDocuments\MyDocuments\NewProjects\Designin Nature Template: C:\Users\Mariska Leunissen\AppData\Roaming\Microsoft\Templates\Normal.dot Title: DesigninNature:Aristotle'sFirstManProblem Subject:  Author: MariskaLeunissen Keywords:  Comments:  CreationDate: 11/14/20101:35:00PM ChangeNumber: 4 LastSavedOn: 11/14/20104:54:00PM LastSavedBy: MariskaLeunissen TotalEditingTime: 199Minutes LastPrintedOn: 11/14/20104:54:00PM AsofLastCompletePrinting  NumberofPages: 23  NumberofWords:8,124(approx.)  NumberofCharacters: 46,313(approx.) 