Having entered into the problem structuring methods, system dynamics (SD) is an approach, among systems’ methodologies, which claims to recognize the main structures of socio-economic behaviors. However, the concern for building or discovering strong philosophical underpinnings of SD, undoubtedly playing an important role in the modeling process, is a long-standing issue, in a way that there is a considerable debate about the assumptions or the philosophical foundations of it. In this paper, with a new perspective, we have explored theory of (...) knowledge in SD models and found strange similarities between classic epistemological concepts such as justification and truth, and the mechanism of obtaining knowledge in SD models. In this regard, we have discussed related theories of epistemology and based on this analysis, have suggested some implications for moderating common problems in the modeling process of SD. Furthermore, this research could be considered a reword of system dynamics modeling principles in terms of theory of knowledge. (shrink)

Antony Flew's ?A Strong Programme for the Sociology of Belief (Inquiry 25 {1982], 365?78) critically assesses the strong programme in the sociology of knowledge defended in David Bloor's Knowledge and Social Imagery. I argue that Flew's rejection of the epistemological relativism evident in Bloor's work begs the question against the relativist and ignores Bloor's focus on the social relativity of mathematical knowledge. Bloor attempts to establish such relativity via a sociological analysis of Frege's theory of number. But this analysis only (...) succeeds if the rejection of an explanatory theory entails that there are reasonable grounds for the rejection of the set of propositions which that theory was intended to explain. I argue against such an entailment, and thus against Bloor's attempt to relativize mathematical knowledge. (shrink)

Knowledge requires both freedom and friction . Freedom to set up our epistemic goals, choose the subject matter of our investigations, espouse cognitive norms, design research programs, etc., and friction (constraint) coming from two directions: the object or target of our investigation, i.e., the world in a broad sense, and our mind as the sum total of constraints involving the knower. My goal is to investigate the problem of epistemic friction, the relation between epistemic friction and freedom, the viability of (...) foundationalism as a solution to the problem of friction, an alternative solution in the form of a neo-Quinean model, and the possibility of solving the problem of friction as it applies to logic and the philosophy of logic within that model. (shrink)

A central problem in epistemology concerns the justification of beliefs about epistemic principles, i.e., principles stating which kinds of beliefs are justified and which not. It is generally regarded as circular to justify such beliefs empirically. However, some recent defenders of foundationalism have argued that, within a foundationalist framework, one can justify beliefs about epistemic principles empirically without incurring the charge of vicious circularity. The key to this position is a sharp distinction between first- and second-level justifiedness.In this paper I (...) first argue that such versions of foundationalism end up giving their approval to circular chains and are therefore unmotivated; if circular chains are acceptable, the classic regress argument for foundationalism does not go through. I then consider and reject two other ways in which the foundationalist might motivate his position. At the end of the paper I draw from this discussion a moral concerning the airns of epistemological theorizing. (shrink)

The background of this paper (section 1) consists in a new account to foundation‐theoretic epistemology characterized by two features: (i) All beliefs are to be justified by deductive, inductive or abductive inferences from a minimalistic class of unproblematic (introspective or analytic) basic beliefs. (ii) Higher‐order justifications for these inferences are given by means of the novel method of optimality justifications. Optimality justifications are a new tool for epistemology (section 2). An optimality justification does not attempt todemonstratethat a cognitive method is (...) reliable (which is impossible), but pursues the more modest goal of demonstrating that the method isoptimalamong all accessible alternative methods for the given epistemic goal. The reasoning from the established optimality of a method to the acceptability of a particular belief generated by the method is accomplished by so‐called optimality principles. In sections 3–5, the method of optimality justifications is carried out in detail for three fundamental problems: justifying induction, logic, and theory‐generating abduction. (shrink)

In this paper a new conception of foundation-oriented epistemology is developed. The major challenge for foundation-oriented justifications consists in the problem of stopping the justificational regress without taking recourse to dogmatic assumptions or circular reasoning. Two alternative accounts that attempt to circumvent this problem, coherentism and externalism, are critically discussed and rejected as unsatisfactory. It is argued that optimality arguments are a new type of foundation-oriented justification that can stop the justificational regress. This is demonstrated on the basis of a (...) novel result in the area of induction: the optimality of meta-induction. In the final section the method of optimality justification is generalized to deductive and abductive inferences. (shrink)

This paper studies degrees of doxastic justification. Dependency relations among different beliefs are represented in terms of causal models. Doxastic justification, on this picture, is taken to run causally downstream along appropriate causal chains. A theory is offered which accounts for the strength of a derivative belief in terms of (i) the strength of the beliefs on which it is based, and (ii) the epistemic quality of the belief-forming mechanisms involved. It is shown that the structure of degrees of justification (...) converges to ranking theory under ideal conditions. (shrink)

En este artículo, el autor examina la tradicional oposición entre el fundacionalismo y el coherentismo como teorías de la justificación, mostrando sus limitaciones y las razones por las que ninguna de ellas puede ser parte de una adecuada teoría del conocimiento. Se sugiere que, para superar esta oposición, es necesario desarrollar una teoría holista de la creencia que, a su vez, permita la elaboración de una teoría holista de la justificación. El artículo consta de tres partes. En la primera, el (...) autor discute las objeciones contra el fundacionalismo, concentrándose en la noción de creencia básica y en la justificación no-doxástica. En la segunda, se examina las objeciones contra el coherentismo. concentrándose en el regreso al infinito del requisito de ascenso épistémico. Finalmente, en la tercera parte el autor aborda el concepto de creencia y la manera como un intérprete atribuye creencias a un agente. También se analiza hasta qué punto es posible reformular la noción de "creencia básica" con el fin de darle un lugar en una adecuada teoría de la justificación. El autor sugiere que el concepto mismo de creencia surge enun contexto intersubjetiva e interpretativo. siendo ese mismo contexto el que va a permitir la justificación de creencias.". (shrink)

This paper responds to Ernest Sosa's recent criticism of Richard Fumerton's acquaintance theory. Sosa argues that Fumerton's account of non-inferential justification falls prey to the problem of the speckled hen. I argue that Sosa's criticisms are both illuminating and interesting but that Fumerton's theory can escape the problem of the speckled hen. More generally, the paper shows that an internalist account of non-inferential justification can survive the powerful objections of the Sellarsian dilemma and the problem of the speckled hen.

One reasonably familiar argument for epistemological scepticism maintains that knowledge requires foundations and that we rarely, if ever, have such foundations. The conclusion of this argument is that we rarely, if ever, have knowledge. A second, less ambitious sceptical argument is that philosophers cannot justifiably say that they have knowledge unless their statement is based on foundations and that we never have such foundations. The conclusion of this argument is not that we never have knowledge, but that philosophers are never (...) justified in saying that they have knowledge. The scepticism is Pyrrhonic, rather than Academic, and merely attempts to counter knowledge assertions, not establish that they are false. It tries to show that in most cases the best response we can give to ‘Do we have knowledge?’ is to remain indifferent. (shrink)

A skeptic claims that I do not have knowledge of the external world. It has been thought that the skeptic reaches this conclusion because she employs unusually stringent standards for knowledge. But the skeptic does not employ unusually high standards for knowledge. Rather, she employs unusually restrictive standards of evidence. Thus, her claim that we lack knowledge of the external world is supported by considerations that would equally support the claim that we lack evidence for our beliefs about the external (...) world. These considerations do not threaten the truth of our ordinary attributions of evidence, however, for such attributions are context-sensitive in their semantics. It is argued that this solution to the problem of the external world enjoys all of the benefits, and suffers none of the problems, of other solutions to the problem of the external world. (shrink)

A skeptic claims that I do not have knowledge of the external world. It has been thought that the skeptic reaches this conclusion because she employs unusually stringent standards for knowledge. But the skeptic does not employ unusually high standards for knowledge. Rather, she employs unusually restrictive standards of evidence. Thus, her claim that we lack knowledge of the external world is supported by considerations that would equally support the claim that we lack evidence for our beliefs about the external (...) world. These considerations do not threaten the truth of our ordinary attributions of evidence, however, for such attributions are context‐sensitive in their semantics.It is argued that this solution to the problem of the external world enjoys all of the benefits. and suffers none of the problems, of other solutions to the problem of the external world. (shrink)

In this paper I want to suggest that causal and interpretive approaches to epistemology are in tension with one another. Drawing on the work of hermeneutic writers I suggest that epistemological justification is an interpretive process. The possibility of rational justification requires attention to our locatedness within the domain of reasons, into which we have been culturally initiated. The recognition that there is no transcendent processes of rational justification has to be addressed from within this framework and cannot be resolved (...) in a naturalizing way. The turn to hermeneutics in the context of epistemology allows us to reassign a central role to experience within epistemological justification. Here the very features of experience which render problematic its role in empiricist accounts form the basis of its position in hermeneutic ones. This presents us with an immanent conception of rationality, in place of the transcendent conception which so many writers have problematized. (shrink)

Foundationalism came under attack in two areas in the first half of this century. First, some doubted whether the foundations were adequate to support the entire structure of knowledge, and second, the doctrine of the Agiven@ came under serious attack. = However, many epistemologists were not convinced that foundationalism was to be abandoned even if the criticisms were granted. According to these epistemologist, far from having shown that foundationalism itself was at fault, the critics of foundationalism had only been attacking (...) one particular version of foundationalism--that version that included infallibility, incorrigibility,, or some appeal to a Agiven@ at the base of the structure of justification. The claim of these defenders was that there are other possible types of foundationalism than this version of foundationalism, which has come to be called Classical Foundationalism. And thus opened up a new area of philosophical lexicography: the attempt to say what foundationalism itself is, so that Classical Foundationalism turned out to be one instance of foundationalism but not the only possible one. (shrink)

In this article, I am concerned with the ethical foundations of behavior therapy, that is, with the normative ethics and the meta-ethics underlying behavior therapy. In particular, I am concerned with questions concerning the very possibility of providing an ethical justification for things done in the context of therapy. Because behavior therapists must be able to provide an ethical justification for various actions (if the need arises), certain meta-ethical views widely accepted by behavior therapists must be abandoned: in particular, one (...) must give up ethical subjectivism, ethical skepticism, and ethical relativism. An additional task is to show how it is possible to provide a nonsubjective, nonskeptical, and nonrelativistic moral justification for an ethical statement. Although this is a monumental task, I provide a rough sketch of such a model, one that is congenial to the value judgments underlying behavior therapy. (shrink)

This essay seeks to clarify the meaning and nature of normativity in metaethics and offers reasons why comparative religious ethics (CRE) must properly address questions about normativity. Though many comparative religious ethicists take CRE to be a normative discipline, what they say about normativity is often unclear and confusing. I argue that the third‐wave scholars face serious questions with respect to not only the justification of moral belief but also the rationality of moral belief and action. These scholars tend to (...) view the justification of moral belief to be a matter of process (that is, discursive social practice) rather than evidence‐possession, thus overlooking crucial differences between the two. They also run the risk of confusing motivating and explanatory reasons with normative reasons for moral belief and action. Consequently, their account of normativity would be insufficient for determining the rationality of moral beliefs and actions as well as for justifying moral beliefs. (shrink)

In his influential paper ‘Two Types of Foundationalism,’ William Alston distinguishes two important conceptions of foundationalism: ‘simple foundationalism’ and ‘iterative foundationalism’. SF is the view that there are immediately justified beliefs of some kind or other. IF is the stronger view that certain epistemic propositions are immediately justified. Alston favors a reliability account of immediate justification of the kind defended by externalists such as Armstrong, Dretske, and Goldman. Alston rejects IF by appeal to what he calls the ‘second level argument.’ (...) He claims, further, that since IF is essential to the Cartesian project of reconstructing knowledge, the Cartesian project must be abandoned. (shrink)

Foundationalism is false; after all, foundational beliefs are arbitrary, they do not solve the epistemic regress problem, and they cannot exist withoutother (justified) beliefs. Or so some people say. In this essay, we assess some arguments based on such claims, arguments suggested in recent work by Peter Klein and Ernest Sosa.

Some foundationalists have argued that epistemic warrant may be in some measure determined by features of a doxastic agent's circumstances that are not necessarily accessible to the agent. 'externalist' views of this sort have been attacked recently by laurence bonjour on the grounds that they are at odds with the ordinary notion of "epistemic rationality". I suggest that this need not be so and argue that bonjour fails to provide convincing reasons for the rejection of externalist forms of foundationalism.

E. Gettier's article "Is Justified True Belief Knowledge?" changed the course of epistemology by analyzing the issue of justified truth regarding propositional knowledge and detecting a problem with the traditional definition of knowledge. The paper discusses various theories on this matter, especially those that highlight foundationalism and coherentism in its internalist aspect.

RESUMO O artigo de E. Gettier, "É Conhecimento Crença Verdadeira Justificada?" mudou o curso da epistemologia ao analisar a questão da verdade justificada pertinente ao conhecimento proposicional e detectar uma falha na definição tradicional de conhecimento, dando origem a diferentes comentários. Várias teorias sobre o assunto são discutidas, sendo as mais utilizadas aquelas que enfatizam o fundacionismo e o coerentismo em seu caráter internalista. ABSTRACT E. Gettier's article "Is Justified True Belief Knowledge?" changed the course of epistemology by analyzing the (...) issue of justified truth regarding propositional knowledge and detecting a problem with the traditional definition of knowledge. The paper discusses various theories on this matter, especially those that highlight foundationalism and coherentism in its internalist aspect. (shrink)

As we trace a chain of reasoning backward, it must ultimately do one of four things: (i) end in an unjustified belief, (ii) continue infinitely, (iii) form a circle, or (iv) end in an immediately justified basic belief. This article defends positism—the view that, in certain circumstances, type-(i) chains can justify us in holding their target beliefs. One of the assumptions that generates the epistemic regress problem is: (A) Person S is mediately justified in believing p iff (1) S has (...) a doxastic reason q for p and (2) S is justified in believing q. Assumption (A) presupposes that reasoning is only justification transmitting, not justification generating. The article rejects (A) and argues that, in certain circumstances, reasoning itself is justification generating, even if that from which one is reasoning is not itself justified. It concludes by comparing positism with its infinitist, coherentist, and foundationalist rivals, acknowledging what is right about these other views. (shrink)

This paper evaluates Peter Klein’s objection to foundationalism. According to Klein, foundationalism fails because it allows arbitrariness “at the base.” I first explain that this objection can be interpreted in two ways: either as targeting dialectical foundationalism or as targeting epistemic foundationalism. I then clarify Klein’s concept of arbitrariness. An assertion or belief is assumed to be arbitrary if and only if it lacks a reason that is “objectively and subjectively available.” Drawing on this notion, I evaluate Klein’s objection. I (...) first argue that his objection construed as targeting dialectical foundationalism fails, since nothing prevents dialectical foundationalism from ruling out arbitrary assertions. I then argue that the objection seen as targeting epistemic foundationalism cannot be disqualified in the way some foundationalists believe. However, I show that also the objection so construed does not succeed, since epistemic foundationalism need not countenance arbitrary beliefs. (shrink)

Religious epistemology is the study of how subjects' religious beliefs can have, or fail to have, some form of positive epistemic status and whether they even need such status appropriate to their kind. The current debate is focused most centrally upon the kind of basis upon which a religious believer can be rationally justified in holding certain beliefs about God and whether it is necessary to be so justified to believe as a religious believer ought. Engaging these issues are primarily (...) three groups of people who call themselves ‘fideists’, ‘Reformed epistemologists’, and ‘evidentialists’. Each group has a position, but the positions are not mutually exclusive in every case, and in the debate, the names better describe the groups' emphases than mutually exclusive positions in the debate. In this article, we will first give a brief historical survey of evidentialism, fideism, and reformed epistemology. Second, we will give the fideist's position. Third, we will give the evidentialist's position. Fourth, we will give the reformed epistemologist's position, and last, we will include some comments on the current state of the debate, where we will show that the groups' positions are not mutually exclusive. (shrink)

I argue—contra moderate grounding pluralists such as Kit Fine and more extreme grounding pluralists such as Jessica Wilson—that there is fundamentally only one grounding/in-virtue-of relation. I also argue that this single relation is indispensable for normative theorizing—that we can’t make sense of, for example, the debate over consequentialism without it. It follows from what I argue that there is no metaethically-pure normative ethics.

Once upon a time, coherentism was the dominant response to the regress problem in epistemology, but in recent decades the view has fallen into disrepute: now almost everyone is a foundationalist (with a few infinitists sprinkled here and there). In this paper, I sketch a new way of thinking about coherentism, and show how it avoids many of the problems often thought fatal for the view, including the isolation objection, worries over circularity, and concerns that the concept of coherence is (...) too vague or metaphorical for serious theoretical use. The key to my approach is to take a familiar tool from discussions of the regress problem -- namely, directed graphs depicting the support relations between beliefs -- and to use that tool in a more sophisticated manner than it is standardly employed. (shrink)

The quantitative problem of old evidence is the problem of how to measure the degree to which e confirms h for agent A at time t when A regards e as justified at t. Existing attempts to solve this problem have applied the e-difference approach, which compares A's probability for h at t with what probability A would assign h if A did not regard e as justified at t. The quantitative problem has been widely regarded as unsolvable primarily on (...) the grounds that the e-difference approach suffers from intractable problems. Various philosophers have proposed that 'Bayesianism' should be rejected as a research strategy in confirmation theory in part because of the unsolvability of this problem. I develop a version of the e-difference approach which overcomes these problems and possesses various advantages (but also certain limitations). I develop an alternative 'theistic' approach which handles many cases that my development of the e-difference approach does not handle. I conclude with an assessment of the significance of the quantitative problem for Bayesianism and argue that this problem is misunderstood in so far as it is regarded as unsolvable, and in so far as it is regarded as a problem only for Bayesians. (shrink)

This paper is an examination of modest foundationalism in relation to some important criteria of epistemic dependence. The paper distinguishes between causal and epistemic dependence and indicates how each might be related to reasons. Four kinds of reasons are also distinguished: reasons to believe, reasons one has for believing, reasons for which one believes, and reasons why one believes. In the light of all these distinctions, epistemic dependence is contrasted with defeasibility, and it is argued that modest foundationalism is not (...) committed to criteria of epistemic dependence on which foundational beliefs are indefeasible. Modest foundationalism is contrasted with coherentism and is shown to be hospitable to a causal criterion of epistemic dependence, compatible with reliabilism, and neutral with respect to skepticism. (shrink)

Immediate knowledge is here construed as true belief that does not owe its status as knowledge to support by other knowledge (or justified belief) of the same subject. The bulk of the paper is devoted to a criticism of attempts to show the impossibility of immediate knowledge. I concentrate on attempts by Wilfrid Sellars and Laurence Bonjour to show that putative immediate knowledge really depends on higher-level knowledge or justified belief about the status of the beliefs involved in the putative (...) immediate knowledge. It is concluded that their arguments are lacking in cogency. (shrink)

As an introduction to explicating the concept of basic knowledge, I shall examine Aristotle's argument for the existence of basic knowledge and urge two basic points. The first point is that Aristotle's argument, properly viewed, establishes the existence of a kind of knowledge, basic or non-demonstrative knowledge, the definition of which does not require the specification of, and hence the satisfaction of,anyevidence condition. This point has been urged by philosophers like Peirce and Austin but it needs further argumentation because most (...) analytic epistemologists still insist thatallknowledge, whether basic or non-basic, requires the satisfaction of some evidence condition. Secondly, to urge that the basic propositions whose existence is established by Aristotle's argument could be privileged but not known, for the reason that there is no evidence condition for them, would be to adopt a position that either entails wholesale skepticism or undermines the basic distinction between knowledge and belief. (shrink)

An encyclopedic article on epistemic supervenience in Blackwell companion to epistemology, 2 ed.

The dissertation examines the nature and epistemic implications of epistemic source circularity. An argument exhibits this type of circularity when at least one of the premises is produced by a belief source the conclusion says is legitimate, e.g. a track record argument for the legitimacy of sense perception that uses premises produced by sense perception. In chapter one I examine this and several other types of circularity, identifying relevant similarities and differences between them. In chapter two I discuss the differences (...) between internalist and externalist analyses of justification. I examine in detail foundationalist and non-foundationalist versions of internalism, and go on to consider how one might characterize externalism: either negatively, by denying particular internalist theses, or positively, in terms of a theory offering different conditions for justification. I discuss the views of reliabilist foundationalists at length. In chapter three I present the internalist objection to externalism that the latter mistakenly permit one to be justified in believing the conclusion of an epistemic source circular inference. I explain the externalists' response that it is not in virtue of their externalism that they permit epistemic source circularity but rather their foundationalism; thus, internalist foundationalists must permit epistemic source circularity as well. I evaluate the positions of several internalists, most of them explicitly foundationalists, and argue that they too cannot avoid permitting epistemic source circularity. In the final chapter I consider whether such circularity is vicious, even though both internalist and externalist foundationalists permit it. I argue that one can sustain an objection to epistemic source circularity by imposing a non-question-begging requirement on justification and explain how respecting this requirement leads one to a non-foundationalist view. I conclude by considering the objection that question-begging leads to a certain arbitrariness in belief formation that should give the foundationalist pause when it comes to determining, at the beginning of inquiry, which beliefs are justified and which are not. The dissertation is primarily concerned with making clear the possible skeptical and non-skeptical positions one can take towards epistemic source circularity. I do not argue for the truth of a particular metaepistemology. (shrink)

This paper is a reconstruction and analysis of Thomas Reid’s epistemology, based upon an examination of his extant manuscripts and publications. I argue that, in Reid’s view, a certain degree of “evidence” (or, as I shall say, ‘epistemic justification’) is that which distinguishes mere true belief from knowledge; and that this degree of justification may be ascribed to a person’s belief if and only if (i) the evidence upon which her belief is grounded is such that she holds it with (...) “certainty”; (ii) she has a “sound understanding”; (iii) she has a distinct conception of the object of her belief; and, finally, (iv) she has formed her belief “without prejudice”. (shrink)

This paper proposes to assess the naturalist project in epistemology with an eye towards exposing the project as deficient for serving as a robust epistemological project. Epistemologists treasure a certain family of questions and burden themselves with a number of specific concerns the most important of which, I think, cannot be answered by the epistemological naturalist. Ignoring these questions, I will argue, essentially amounts to a dismissal of the principle tension that primarily motivates and properly guides epistemological theorizing. This tension (...) is the familiar appearance vs. reality distinction and characterizes what I am calling the classical landmark or boundary-stone for epistemological theorizing. I will defend the claim that a full replacement of the traditional/classical epistemological project by a naturalized epistemology closes epistemology off from making important claims needed in a theory of human knowledge and, for that reason, a full replacement should be resisted. These claims that an epistemology should be expected to make issue from what I call the classical landmark for epistemological inquiry. Naturalist's effectively ignore this landmark and I caution them in the spirit of the proverb to not "remove the ancient landmark which your fathers have set. (shrink)

Most epistemologists agree that epistemic justification is required for knowledge. This requirement is usually formulated in one of two ways: S knows that p only if S is justified in believing that p. S knows that p only if S's belief that p is justified. Surprisingly and are generally regarded as synonymous formulations of the justification condition. In Chapter 1, I argue that such a synonymy thesis is mistaken and that, in fact, and specify substantively different requirements. requires that the (...) person be justified, whereas requires that the belief in question be justified, and intuitively, these constitute different requirements. Thus, it is concluded that and employ inherently different kinds of epistemic justification in their respective analysantia. I dub them "personal justification" and "doxastic justification", respectively. The remainder of the dissertation is devoted to demonstrating both the legitimacy and the importance of the personal/doxastic justification distinction. For example, the distinction helps account for the divergent intuitions that regularly arise regarding justificatory evaluations in demon-world contexts. ;In Chapters 2 and 3 I provide analyses for doxastic and personal justification. Chapter 2 spells out an externalist reliabilist account of doxastic justification which safely avoids demon-world counterexamples. Chapter 3 advances an internalist coherence account of personal justification. In defending this coherence theory, I argue that all foundation theories are false and that the regress argument on which they are predicated is unsound. ;In Chapter 4, I propose an analysis of ordinary knowledge which only requires doxastic justification. Nevertheless personal justification plays a negative, undermining role in the analysis. I then demonstrate that this analysis of knowledge is immune to typical Gettier examples. It also remains unscathed by Harman's beefed-up Gettier cases. Finally, I consider a stronger analysis of knowledge requiring both doxastic and personal justification. Though the latter analysis proves too strong for ordinary knowledge, it remains interesting as an analysis of a more intellectualistic kind of knowledge. ;The final chapter examines the internalist/externalist controversy and demonstrates that this controversy is yet another manifestation of the personal/doxastic justification conflation. (shrink)

This dissertation examines Rene Descartes' view of certainty and defends the view that Cartesian certainty is possible. The first half of the dissertation includes an interpretation of Descartes' epistemology as well as an examination of other interpreters' readings. The second half of the dissertation is a defense of the claim that Cartesian certainty of a particular kind is possible; it includes a variety of contemporary objections and replies in defense of the possibility of certainty.