Page | 1 Is Hume a Causal Realist? A (Partial) Resolution of the 'Two Definitions of Cause Dispute' in Hume's Account of Causation Stephen John Plecnik I. Introduction In A Treatise of Human Nature I.iii.14 entitled, Of the idea of necessary connexion, Hume sets out to examine "one of the most sublime questions in philosophy, viz. that concerning the power and efficacy of causes" (THN 1.3.14.2). According to Hume, the study of causation is the most "obscure and uncertain" (EHU 7.1.3) field in metaphysics, but the payoff from such an investigation is certainly worthwhile, especially if by the end we are able to "form an exact definition of the relation of cause and effect" (THN 1.3.14.30). Out of all of the Sections in the Treatise, Section 14 is the one that has received some of the most scholarly attention, and for good reason: Hume's views on causality are often taken to be the unofficial centerpiece or hallmark of his entire philosophy. The secondary literature that deals with this Section abounds with countless interpretations of what Hume really meant when it came to causation and raises many important questions that we should ask of Hume's position. Some of the more important questions asked in the scholarly literature are: 'Is Hume a causal realist?,' 'Are Hume's two definitions of the term cause truly adequate definitions?,' 'Does Hume view one of his two definitions of cause as being more fundamental than the other?,' etc. And there are many more. Of course, it will be impossible for this paper to consider all of the important work and questions pertaining to Hume's account of causation; this is inevitable and not unexpected. As a result, I will focus my attention on two major interrelated questions/points. First, I will ask and attempt to answer the question, 'Is Hume a causal realist?' This question has received a great deal of attention as of late from Hume scholars, and from just a Page | 2 cursory glance at the research done on this question, one can see that it is far from being settled. On the one hand, many scholars (like Michael Costa, Norman Kemp Smith, John P. Wright, etc.) believe that Hume endorses a causal realist position in both the Treatise and Enquiry. They argue that there is strong evidence to support the view that Hume (and everyone else) must, through the nagging forcefulness of nature, believe in the existence of objective causal relations that exist independent of the mind. According to them, the belief in objective causal relations is like the belief in external objects, in that we must have this belief in order to navigate through our lives in a socially intelligent way. Thus, being a causal realist is a natural inevitability and everyone, including Hume, would by nature be a causal realist. Kenneth P. Winkler calls these scholars the defenders of the "New Hume" (Winkler 550). On the other hand, other scholars (like Winkler, W. Knight, H. A. Aikins, etc.) think that Hume is best interpreted as being a causal anti-realist. Working under this causal anti-realist interpretation, they claim that Hume believes the only type of meaningful/reasonable account of causation is one in which the power of causes rests wholly in the human mind; not in anything external. These followers of the "Old Hume" back up their claim by pointing to the large amount of textual evidence that lends support to such a subjective interpretation of Hume's account of causation. For example, Hume states clearly that "the necessity or power, which unites causes and effects, lies in the determination of the mind to pass from one to the other. The efficacy or energy of causes is neither plac'd in the causes themselves, nor in the deity, nor in the concurrence of these two principles; but belongs entirely to the soul, which considers the union of two or more objects in all past instances. 'Tis here that the real power of causes is plac'd, along with their connexion and necessity" (THN 1.3.14.23, emphasis mine). It seems relatively clear from this quote (and many others like it), that for Hume the real power of causes is placed Page | 3 'entirely' in the human soul. There is no mention here of the possibility that some objects (causes) could support their own causal relations with other objects (effects); in fact, Hume expressly denies in the above quote that such a thing would be possible. The efficacy of causes is not placed in (1) the causes themselves, (2) the Deity, or (3) in the agreement of causes with the Deity. It is placed in us alone. Based on such overwhelming textual evidence, I will argue the traditionalist route that Hume is better seen as being a causal anti-realist. Second, this paper will try to partially resolve what is aptly called the 'two definitions of cause dispute.' The origin of this dispute is well-known. In both the Treatise (THN 1.3.14.31) and Enquiry (EHU 7.2.29), Hume infamously gives not one, but two definitions of the term cause. Ever since, scholars have wondered why he came up with two non-equivalent definitions of the same cause and effect relation. I believe that the way we can ultimately make sense of this ambivalence present in Hume's thought is by gaining a definitive answer to the first, and major, question of this paper: Is Hume a causal realist? Given the answer to this question, I think we will be able to resolve, at least partially, the two definitions of cause dispute. Resolving this dispute will come down to being able to show which one of the two definitions of cause is more fundamental than the other, i.e., which one of the definitions-be it the philosophical definition of the cause and effect relation or the natural definition of the cause and effect relation-more fully captures the essence of causation according to Hume. If we come to the conclusion that Hume is a causal anti-realist (which is the position I am supporting), then this will determine which of the two definitions of cause is primary. Specifically, it will show us that Hume is more favorably disposed toward accepting the natural definition of the cause and effect relation as the more accurate of the two. If the New Hume movement, however, is correct in labeling Hume as Page | 4 a causal realist, then this would provide strong evidence for Hume favoring the first, philosophical definition of cause as primary. II. Is Hume a Causal Realist? Before we can answer the question, 'Is Hume a causal realist' with any kind of finality, it will first be necessary to lay out Hume's major argument in Section 14 of the Treatise. Recall that in Book I, Part iii, Section 14 of the Treatise, Hume is trying to show us where our idea of necessary connection comes from; incidentally, he does the exact same thing in Section 7 of the Enquiry, albeit in a much more succinct way. Following his theory of ideas, Hume states that we must look for the idea of necessary connection or the cause and effect relation (they are the same idea according to Hume) in our impressions, "from which it is originally deriv'd" (THN 1.3.14.4). If we cannot find an impression of the cause and effect relation, then we cannot say in any legitimate, philosophical sense that we have an idea of it. It is important to note that throughout the Treatise and Enquiry, Hume is steadfastly consistent when it comes to obeying his famous 'Copy Principle:' "We have established it as a principle, that as all ideas are deriv'd from [or copied from] impressions, or some precedent perceptions, 'tis impossible we can have any idea of power and efficacy, unless some instances can be produc'd, wherein this power is perceived to exert itself" (THN 1.3.14.10). Thus, based on Hume's account of ideas and how they come to exist in our minds, he must say that the idea of necessary connection, power, force, efficacy, etc. arises from some impression. One will remember that, for Hume, there are two kinds of impressions: sense impressions and impressions of reflection. The idea of cause and effect, therefore, must originate in either a sense impression (external impression) or an impression of reflection (internal impression). Page | 5 Though the following passage is a bit lengthy, it clearly sums up Hume's argument that the idea of necessary connection must originate in an impression of reflection; not an impression of sense: "The idea of necessity arises from some impression. There is no impression convey'd by our senses, which can give rise to that idea. It must, therefore, be deriv'd form some internal impression, or impression of reflection. There is no internal impression, which has any relation to the present business, but that propensity, which custom produces, to pass from an object to the idea of its usual attendant. This therefore is the essence of necessity. Upon the whole, necessity is something, that exists in the mind, not in objects; nor is it possible for us ever to form the most distant idea of it, consider'd as a quality in bodies. Either we have no idea of necessity, or necessity is nothing but that determination of the thought to pass from causes to effects and from effects to causes, according to their experienc'd union" (THN 1.3.14.22, emphasis mine). There is a lot to unpack in this quote. The first important thing to note in this passage is the very brief and direct argument that Hume presents to show that the idea of necessary connection originates in the mind alone and not from anything external, i.e., from physical objects/events. He argues that (P1) 'The idea of necessity arises from some impression.' (P2) 'There is no impression convey'd by our senses, which can give rise to that idea.' (C) 'It must, therefore, be deriv'd form some internal impression, or impression of reflection.' The argument is quite simple, but it is worth explaining to some extent, as I think this argument will eventually help prove that Hume is best interpreted as being a causal anti-realist. Clearly, Hume wants us to see (P1) as a necessarily true statement based on his 'Copy Principle.' For Hume, the idea of necessity must be copied from some impression, since all ideas (which are not mere flights of the Fancy) must be able to be traced back to their correspondent impressions which gave rise to them. This is one of the foundational principles that supports his entire empiricist position. So far, what Hume has to say is relatively uncontroversial. When we move on to consider (P2), however, here is where some of us may have a problem with what Hume has to say. Is it really true that there is no impression conveyed by our senses which can give rise to Page | 6 the idea of necessary connection? Hume certainly thinks so, and the way in which he argues for the truth of this premise is, in my opinion, quite clever and ingenious. To justify the truth of this premise, Hume basically tells us to go out into the world and observe two or more objects that are, generally and for the most part, conjoined in experience (e.g., fire and heat). Then he asks us: When you observed those two or more objects, did you experience through your sensitive faculties any necessary connection in them? We, of course, would have to say no, as we can "never observe [this] in them, but must draw the idea of it from what we feel internally in contemplating them" (THN 1.3.14.28). Hume thus proves the truth of (P2) by showing us the experiential impossibility of observing a necessary connection in objects. If we grant that these two premises are both true, (which, I think, we would all be willing to allow), then it necessarily follows that (C) the idea of necessary connection must be derived from some impression of reflection. At this point, we might well ask: What is the big deal? So what if the idea of necessity is derived from an impression of reflection? The importance of this short argument, however, should not be underestimated. By proving that the idea of the cause and effect relation originates in the mind alone, and not in any external objects, Hume has shown that necessity rests solely in the mind of the human knower (the perceiver). Nothing external or mind-independent can give rise to our idea of necessity. In other words, everything that is essential for us to form the idea of necessity is already present within our mental and psychological apparatus. It is not the actual link-up of two or more physical objects in experience that provides us with an idea of necessity; rather, it is that propensity of the mind- which custom produces-to move from one object to the idea of its usual attendant that produces such an idea. As Hume said in the earlier quote, "necessity is something, that exists in the mind, not in objects; nor is it possible for us ever to form the most distant idea of it, consider'd as a Page | 7 quality in bodies" (THN 1.3.14.22). Even scholars like Costa, who want to interpret Hume as being a causal realist, cannot deny that he placed necessity in the human mind alone and nowhere else: "There is little controversy about whether Hume thinks that we can rationally justify attributing causal powers to objects-he clearly thinks we cannot" (Costa 175). Later on in this paper I will more fully explicate Costa's argument for causal realism, but for now we shall continue on with what Hume has to say concerning causation. For Hume, necessity is not something that exists in nature or any of its animate or inanimate inhabitants; it is something that exists in Human Nature! Considering that Hume's entire goal in the Treatise is to show that the science of Human Nature is the foundational science from which all of the others originate, it seems plausible that Hume would defend such a radical view of causality: A view of causality which places at its center human nature, and, specifically, the human mind. Even more evidence that tips the scales in favor of my interpretation of Hume as being a causal anti-realist (one who believes that causal relations are completely subjective and supported by the mind), is found when Hume considers a possible objection to his minddependent view of causation. Hume notes that: "But tho' this be the only reasonable account we can give of necessity, the contrary notion is so riveted in the mind from the principles above-mentioned, that I doubt not but my sentiments will be treated by many as extravagant and ridiculous. What! The efficacy of causes lie in the determination of the mind! As if causes did not operate entirely independent of the mind, and wou'd not continue their operation, even tho' there was no mind existent to contemplate them, or reason concerning them. Thought may well depend on causes for its operation, but not causes on thought. This is to reverse the order of nature, and make that secondary, which is really primary" (THN 1.3.14.26). From the quote, one can see Hume is quite clear in saying that the only reasonable account we can give of necessity is the one that highlights the dependence of the cause and effect relation on the mind. Of course, he realizes that his subjective account of the cause and effect relation will meet its fair share of criticism from those who still hold on to the common (or 'vulgar') view of Page | 8 causation; the vulgar will not hesitate to treat his sentiments on this sublime philosophical topic as 'extravagant' and 'ridiculous.' It is interesting to note that the 'vulgar' men and women that Hume had in mind here no doubt included the common folk of his day, but also most, if not all, Western philosophers. When it comes to causation, Hume represents a fundamental break with his philosophical predecessors and contemporaries in that he puts forth a non-object-centric view of causality. Unlike most philosophers, Hume believes that the only true account of causation which can be offered is one in which the foundational role of Human Nature is acknowledged. Hume, then, appears to be showing the difference between his anthropocentric view of causality and the object-centric view of causality that he is attacking: "He is drawing a contrast between his view, that necessity exists in the mind, and the view that he is attacking, that necessity exists in matter or bodies. Clearly the 'objects' which Hume has in mind are physical objects or bodies" (Russell 14). The fundamental source of this dispute between Hume and the vulgar is grounded in a bias of the mind from which Hume was apparently strong enough to free himself. Hume argues that the contrary notion of necessity (necessity as existing in objects) is fixed in the mind 'from the principles above-mentioned.' So what are these principles which cause such a prejudice in the mind to see objects as the true bearers of the cause and effect relation? For Hume, "'Tis a common observation, that the mind has a great propensity to spread itself on external objects, and to conjoin with them any internal impressions, which they occasion, and which always make their appearance at the same time that these objects discover themselves to the senses...the same propensity is the reason, why we suppose necessity and power to lie in the objects we consider, not in our mind, that considers them" (THN 1.2.14.25). Thus, the vulgar incorrectly apply the internal impression of necessity to the external objects that they experience, thereby leading them Page | 9 to believe that it is the objects themselves, and not their minds, that support the cause and effect relation. Hume, though, wants us to check such biases of the mind and correctly observe that the internal impression of necessity is not something that we can ever receive from external objects. Once we can throw out such prejudices, and see that the cause and effect relation solely depends on our minds, we can finally come to embrace the true account of causation. Interestingly enough, I think that Hume's description of this hypothetical objection also provides a good clue as to what type of causal realism Hume is arguing against. Hume claims that the average person will have a problem with his position on causation because he seems to 'reverse the order of nature' by calling causes dependent on the mind. Any 'normal' person would claim that this is absurd; clearly causes are not dependent on the mind and would continue to exist even if there were no mind to perceive them. No one actually believes the world, nature's laws, relations, objects, etc. are destroyed once we (or some other being or beings would) stop perceiving them! It is not much of a stretch at all to claim that the vulgar position here could be equated with the causal realist's position. What I mean to say is the common view of causality mentioned by Hume seems to fit nicely with what is usually seen as the causal realist's position. Typically, causal realism is defined as some kind of combination of causal objectivism and power realism: "(1) causal objectivism (causes are objective in the sense that causal relations would continue to hold among events in the world even if there were no minds to perceive them), and (2) power realism (objects stand in causal relations because of the respective causal powers in the objects)" (Costa 174). Just a quick glance at the aforementioned objection that Hume considers should make it evident to us that he is arguing against causal realism (understood as a conjunction of causal objectivism and power realism) in Section 14 of the Treatise. Presumably, Hume would also take issue with Page | 10 a causal realist who only claimed to support one of these two positions by itself, e.g., a causal realist who only subscribed to causal objectivism, but not power realism. First of all, Hume disagrees that causes operate entirely independent of the mind; we have seen that the only causes that can truly 'operate' for us are the ones that exist in our minds. Any other kinds of (secret) operational causes must necessarily be outside the realm of human understanding and reasoning. Secondly, he does not think that causes-at least the ones that are relevant to us, i.e., the ones which we can experience through an internal impression-would continue to exist if there were no mind to perceive them. According to Hume, if a cause is to exist for us, then it must be perceived. I emphasized the words 'for us' in the preceding sentence, because I think it is important to acknowledge that Hume never explicitly denies that there may be cause and effect relations that hold in nature among objects independently of their being perceived. It is best to say that Hume was agnostic when it came to the belief in secret causes that operate outside our perception of them. Hume would no doubt say that such unperceived necessary relations may exist, but we will never know, as we can never perceive them. Epistemologically speaking, then, these objective causal relations that supposedly take place in nature are unknowable, and, hence, of little concern to philosophers and natural scientists. Some followers of the New Hume movement take this agnosticism on the part of Hume as a way to help bolster their causal realist interpretation of him. For example, Norman Kemp Smith writes, "What [Hume] intends to assert is not that there is no such thing as necessity or agency outside the mind, but that the only meaning which we can attach to the terms 'necessity,' 'agency,' 'power,' 'energy,' is one which derives from what is no more than a feeling" (Kemp Smith 397). One can see that this kind of qualification of Hume's position by Kemp Smith is not only acceptable, but also useful in that it helps us to avoid mischaracterizing Hume's account of Page | 11 causality. Hume is not making any dogmatic claim that there is no such thing as necessity or agency outside of the mind; in fact, he leaves open the possibility that there may be, but we can never know for sure. I myself am perfectly willing to allow that Hume may have thought that it was possible there was a .000000001 chance that nature had its own intrinsic causal structure independent of human thought and reasoning. But in acknowledging all of this, we must not forget the major epistemic problem that the causal realists desire to get past our attention: If there is a necessity that exists outside of the mind, and if we can attach no meaning to this kind of necessity, then it does not, epistemologically speaking, exist for us. Perhaps an analogy involving Hume's view of miracles will help to clarify this latter point. Like a miraculous event, an objective necessity may exist, or may come to exist, in nature; there is nothing logically contradictory or metaphysically impossible about its existence. Claiming that mind-independent cause and effect relations could exist in nature is not like saying wooden iron, square circles, or married bachelors could come to exist in nature. It is possible for the former to exist, but not any of the latter three. But unlike a miracle, which "may either be discoverable by men or not" (EHU n.23), objective causal relations can never be discovered through the use of our sensitive faculties. Hume does not waver on this point. Recall that, for Hume, the idea of necessity is derived from an internal impression of the mind, and not an external impression of the senses. It follows from all of this that we have a better chance of discovering a miracle than we do objective necessity, since we have absolutely no possibility of epistemic access when it comes to a necessity that subsists outside of the mind. The impression of an objective cause and effect relation simply cannot be received and processed by our sensitive organs, which, of course, precludes us from ever having an idea of it. Page | 12 The major problem here is that by closing off our epistemic access to an objective necessity or agency that exists out there in nature, Hume, for all practical purposes, makes such an objective necessity irrelevant for philosophical and scientific discourse. If we cannot receive an external impression of this objective necessity-and Hume explicitly claims that no such impression is conveyed to us by our senses-then there is no reason to even talk about it; it would literally mean nothing to us. Costa even admits that "insofar as we have a concept of causal power that represents something of which we can have some knowledge, it is a concept only of a subjective internal impression. We can use the term 'power' to signify objective features of the external world, so long as we recognize our inability to conceive ('ideate') those qualities" (Costa 181). I believe that the above comments of first, Kemp Smith and then, Costa -two supporters of the realist interpretation of Hume-are very telling; not even they say that we can know of these objective causal powers that may exist in objects. The only idea of necessity that we can have is given to us from an internal impression of a determination of the mind to pass from one idea to its usual attendant. Winkler puts it nicely when he states that Hume's account of necessity as being minddependent is decisive, while at the same time not being dogmatic: "Necessity as we understand it lies entirely in the mind. We can't even think or wonder about it as it exists in objects. This cuts off belief in objective necessary connection (that is why it is "decisive") without positively denying its existence (that is why it is not "dogmatic")" (Winkler 576). Though Winkler has taken some heat in the scholarly literature (cf. John Wright 88) for claiming that 'we cannot think or wonder about objective necessity,' and that we cannot believe in objective necessary connections (which does not seem to be correct, as many of the vulgar clearly do), I think his major point still stands: The only type of necessity we can understand is placed wholly in our Page | 13 minds. There may indeed be another kind of objective necessity-Hume never openly denies this possibility-but we will never come to know it. At this point, we should clearly see the difficulty that the causal realist wants to ignore. Based on our lack of epistemic access to the idea of an objective necessity, there is no way to proclaim with any kind of certainty that Hume was a causal realist; in fact, no one, including Hume, could ever say in a legitimate, philosophical sense that he/she was a causal realist because of the limitations of our sensitive faculties, which do not allow us to gain an external impression of the power, efficacy, energy, etc. of causes. Simply put, Hume lives and dies by his 'Copy Principle': No impression of objective necessity = no idea of objective necessity. Even though the evidence seems stacked against them, defenders of the New Hume still argue that there is a textual basis for interpreting Hume in the way that they do; and it is only fair that we should consider this evidence to see if some kind of a case can be made for their causal realist reading of Hume. Winkler notes that "[n]early every defender of the New Hume quotes the following passage from the Treatise (Kemp Smith (1941, p.398); Wright (1983, p.132); Costa (1989, p.180); Broughton (1987, pp.227, 236); and Edward Craig (1987, p.103))" (Winkler 550) to justify their reading: "I am, indeed, ready to allow, that there may be several qualities both in material and immaterial objects, with which we are utterly unacquainted; and if we please to call these power or efficacy, 'twill be of little consequence to the world. But when, instead of meaning these unknown qualities, we make the terms of power and efficacy signify something, of which we have a clear idea, and which is incompatible with those objects, to which we apply it, obscurity and error begin then to take place, and we are led astray by a false philosophy. This is the case, when we transfer the determination of the thought to external objects, and suppose any real intelligible connexion betwixt them; that being a quality, which can only belong to the mind that considers them" (THN 1.3.14.27). Immediately we should ask ourselves: What in this quote would lead those who support the New Hume to claim that Hume is a causal realist? At no point in this passage does Hume ever Page | 14 contradict what he had said before concerning the vulgar conception of causation; he never says that there could be knowable cause and effect relations that operate independently of the mind's perceiving them. All he says is that he is willing to allow for the possibility of there being several unknown qualities that may inhere in both material and immaterial objects. The qualifications that Hume makes here are important, and, I believe, show that he is clearly not arguing for the justification of causal realism. Granted, Hume admits that there may be these unknown qualities in objects, and if we want to call these power and efficacy, then he says fine...you can most certainly do that; but it 'will be of little consequence to the world.' According to Hume, then, just arbitrarily saying that these terms reference unknown qualities will have no consequence for either philosophy or natural science (or any other significant discipline), so why even bother with such abstruse speculations. We must only trust our impressions and any ideas that can be traced back to said impressions. If we go any farther than that, then we go beyond the reach of human understanding. We may conclude that this quote at best shows that Hume is agnostic when it comes to the existence of objective necessity: It may exist, it may not. One can assume, however, that Hume believes the odds are not in favor of its existence, because such an impression is not subject to the principle of (empirical) verification; in fact, I would argue that the quote just mentioned actually provides support for the traditionalist interpretation of Hume. Hume is very clear in stating that we are 'led astray by a false philosophy' whenever 'we transfer the determination of the thought to external objects, and suppose any real intelligible connexion betwixt them; that being a quality, which can only belong to the mind that considers them.' Hume then reasons that the terms power and efficacy have no meaning for us when they are either applied to unknown qualities in physical objects or when they are applied to supposedly Page | 15 known qualities in external objects. In the former case, power and efficacy contain no meaning for us because we let these terms denote unknown qualities, i.e., empty classes with nothing in them. In the latter case, power and efficacy have no meaning for us because we falsely let them signify things we cannot empirically know through our senses. In both of these cases, Hume has shown that power and efficacy in regards to external (mind-independent) objects are topics best left alone, thereby providing definitive evidence against the causal realism of, say, Costa or Kemp Smith. Only when we are talking about causality in relation to that 'determination of the thought' does necessity make any philosophical sense. The New Hume supporters now seem to be backed into a corner. The textual evidence they presented can, at best, only show Hume to be an agnostic in regards to knowledge of objective cause and effect relations, whereas the textual evidence given on the side of the supporters of the Old Hume seems to be decisive and straightforward in proving Hume to be a causal anti-realist. But before we condemn the New Humeans for making a grand mistake in their interpretation of Hume, we should consider one more key (and mostly non-textually based) argument that they have in their arsenal: "According to most defenders of the New Hume, causal realism is an inevitable natural belief... If they are right, we have powerful evidence of Hume's causal realism: if he believes that everyone is by nature a causal realist, Hume is presumably one himself. It is possible to hold this view even if one supposes, as Costa does, that Hume takes belief in causal realism to be entirely unjustified (1989, p. 175)" (Winkler 561-562). As we know, Hume thinks that we are completely unjustified from an empiricist standpoint to attribute an objective existence to causes and to believe that such causes have their own (secret) efficacious powers. Hume straightforwardly denies the theses of causal objectivism and power realism, respectively. This denial, however, Costa and others would argue, does not preclude the possibility of causal realism being an inevitable natural belief that we must all share due to the Page | 16 impositions of nature. Their main argument for causal realism is as follows: (P1) There are some beliefs (like the belief in an external world, the belief in physical objects, the belief that the future will resemble the past, etc.) that cannot, by the intervention of nature, be doubted. We need these beliefs to function in society, and nature forces us to hold on to these beliefs no matter how much we philosophize to the contrary. (P2) The belief in objective necessary connections is one such inevitable natural belief that all human beings must possess by nature; nature forces us to psychologically accept this belief, even though it has no epistemic justification. (C) Therefore, we must believe in objective necessary connections. There are problems, however, present in this argument. For one thing, while our beliefs in an external world and physical objects could be seen as being inevitable, natural beliefs, it does not follow from this that belief in objective necessary connections is equally inevitable. One can see here that I am specifically taking issue with (P2) of the causal realist's argument- that our belief in objective necessary connections is on par with our belief in an external world, belief in physical objects, and the belief that the future will resemble the past. It is not at all clear, for example, that belief in an external world possesses the same psychological force as belief in objective necessary connections. To me, at least, belief in an external world is necessary to function in this life in a socially intelligent way, but it is far from obvious that belief in objective cause and effect relations is similarly necessary. We do not need belief in objective causal relations to act in the way that we do every day: "Our inductive expectations, which are necessary for life, are (so far as we know) entirely independent" (Winkler 564) of this belief. Furthermore, Hume proves throughout the entire Treatise (and especially in Book I.iv.1, where he shows even relations of ideas can be called into doubt!) that any belief we have can be doubted. Certainly nature may eventually force us to pick back up some of these essential Page | 17 beliefs when we come out of our studies into the real world, like our belief in external objects, but there is no reason to think that belief in objective necessity is either as psychologically irresistible or necessary for life as these other essential beliefs. Belief in an objective necessity not only seems capable of being suspended in "special or isolated circumstances" (Winkler 562), like when we are philosophizing in our armchairs, but it seems to be capable of suspension even when we are living our normal, everyday lives. Thus, I would argue that there is strong evidence to reject the causal realist's argument that everyone is, by nature, a causal realist, as "there is simply no evidence that Hume takes causal realism to be an inescapable belief" (Winkler 562). III. The Two Definitions of Cause Dispute Now that we have answered the major question of this paper, 'Is Hume a causal realist?,' in the negative, and have given strong evidence to prove that Hume is a causal anti-realist, I will proceed to lay out and briefly explain Hume's two non-equivalent definitions of cause. Then, in the final section of this paper, I will show that Hume, being a causal-antirealist, must have favored one of these two definitions above the other. As I mentioned at the outset of this paper, in the Treatise I.iii.14 (and in Section 7 of the Enquiry), Hume's goal is to "form an exact definition of the relation of cause and effect" (THN 1.3.14.30). But instead of giving us one precise definition of the cause and effect relation, Hume gives us two imperfect definitions of the cause and effect relation. Clearly, therefore, Hume failed in the self-assigned task which he set himself. This failure, and the ambivalence which resulted from it, has, of course, spawned a great dispute in the secondary literature dealing with Hume's account of causation known as 'the two definitions of cause dispute.' Generally speaking, the dispute turns on a few important questions, like 'Why did Hume give two definitions of cause in the first place?,' 'Is one of these two definitions more important than the Page | 18 other?,' 'Is Hume endorsing both of these definitions of cause?,' etc. Before we can answer some of these questions and (partially) resolve the dispute, we must first closely examine the two following definitions of cause which Hume gives in the Treatise: Definition (C1): "We may define a CAUSE to be 'An object precedent and contiguous to another, and where all the objects resembling the former are plac'd in like relations of precedency and contiguity to those objects, that resemble the latter" (THN 1.3.14.31). Definition (C2): "A CAUSE is an object precedent and contiguous to another, and so united with it, that the idea of the one determines the mind to form the idea of the other, and the impression of the one to form a more lively idea of the other" (THN 1.3.14.31, emphasis mine). After listing the two definitions, Hume immediately goes on to say that both of these definitions of cause are imperfect and defective, because they are "drawn from objects foreign to the cause" (THN 1.3.14.31). "Hume's definitions of causality are clearly presented as definitions which are wholly inadequate to what they purport to define" (Wright 91). Further textual evidence that Hume was dissatisfied with these definitions can be found in the Enquiry, where he says, "Yet so imperfect are the ideas which we form concerning it [i.e., the cause and effect relation], that it is impossible to give any just definition of cause, except what is drawn from something extraneous and foreign to it" (EHU 7.2.29). Thus, it is obvious that Hume was not completely happy with the formulations of these two definitions of cause, but it would be a mistake, I think, to claim that he did not take them seriously, or that he thought they were utterly useless in helping to delimit the essence of causality. Hume is confident that while his two definitions of the cause and effect relation are not perfect, they still must each capture something of the essence of cause. Right before he gives his two infamous definitions, Hume provides a bit of a disclaimer: "There may two definitions be given of this relation, which are only different, by their presenting a different view of the same object, and making us consider it either as a philosophical or as a natural relation; either as a comparison of two ideas, or as an association betwixt them" (THN Page | 19 1.3.14.31). These are clearly not the words of someone who is utterly dissatisfied with his philosophical work. According to Hume, both definition (C1), which is the philosophical definition of the cause and effect relation, and definition (C2), which is the natural definition of the cause and effect relation, capture something important about the notion of cause; maybe they do not capture the total intensional and extensional meaning of causation, but they do an adequate job explaining how we-philosophers and vulgar alike-think about causation. The next logical question to ask is: What, if anything, is the major difference between these two definitions? What does (C1) capture that (C2) does not and vice versa? One will notice that I emphasized some key words in definition (C2) above, namely, idea, mind, and impression. Such words are conspicuously absent in definition (C1), and it seems like Hume must have done this for some reason. At least this kind of a radical change from the philosophical language of 'objects' to the 'mental' language of minds, impressions, and ideas should not go unnoticed by us. This kind of a shift in perspective from objects to minds and their perceptions seems to indicate that these two definitions are not equivalent in meaning, i.e., they do not dovetail or come together in any significant way; these are two non-equivalent and non-substitutable definitions of one and the same thing-causation. Along with James Lesher (cf. J.A. Robinson 164), I believe that (C1) and (C2) differ in regards to both (1) their intensional meaning and (2) their extensional meaning: "(1) That [C1] and [C2] differ in meaning is obvious from the consideration of ideas and the determination of the mind in [C2] and the absence of any such notions in [C1]. (2) That they pick out different events as causes is shown by Hume's admission of 'secret causes' which satisfy the conditions of temporal precedence, contiguity, and constant conjunction of [C1] but, as they are unobserved, fail to be conditions of psychological associations for any observer as required in [C2]" (Lesher 388). It appears, therefore, that Hume is offering two radically different accounts of causality. The philosophical definition of cause employs a marked use of the 'object' language to define what a Page | 20 cause is, and never once mentions ideas, impressions, or minds. It also picks out external objects/events as causes, which, as we know, are unobservable under Hume's epistemological system; recall that only perceivable existents, i.e., one's perceptions (impressions/ideas), are capable of being observed by the mind. The natural definition of cause, on the other hand, uses more of what I would call a 'mental' language, including the concepts of ideas, impressions, and minds. Unlike the philosophical definition, it does not allow objects to be causes; instead, it only allows observable mental existents, like impressions and ideas, to be causes of other impressions and ideas. We can surmise from all of this that, for Hume, philosophical relations are relations among objects, whereas natural relations are relations among perceptions. It seems fair to conclude that Hume's first definition of cause (C1) is "an account of causation as it exists in the material world independent of our thought and reasoning," and his second definition of cause (C2) is "an account of causation as we find it in our perceptions" (Russell 1-2). Now the question is: which one of these two accounts more fully captures the essence of causation according to Hume? If we can answer this question, and if we can prove that one of these two definitions is more fundamental than the other, then the two definitions of cause dispute will be, at least partially, resolved. Why? Because showing that Hume really endorses or favors one of his two definitions above the other will do away with the dispute's major fuel and strength, i.e. the faulty belief that these are two dueling definitions that carry equal weight in Hume's philosophy of Human Nature. IV. A (Partial) Resolution of the Two Definitions of Cause Dispute Given all of the information we have amassed up to the present, it seems relatively clear which one of the two definitions of cause Hume favors: Definition (C2)-the definition of the cause and effect relation as a natural relation. The reason for this is clear. According to Hume's Page | 21 theory of ideas, we only have epistemic access to what we can perceive, and we can only perceive impressions and ideas. Though the following may sound strange to many realists, who believe in the real existence of external objects, Hume does not think we can be fully certain that external objects exist in nature; they probably exist, but we can never be sure, as they are not able to be perceived by us. Hume states that the "only existences, of which we are certain, are perceptions, which being immediately present to us by consciousness, command our strongest assent, and are the first foundation of all our conclusions" (THN 1.4.2.47, emphasis mine). As one would expect, this epistemological claim has far-reaching consequences for Hume's philosophy. By effectively cutting out objects from the realm of potentially knowable things, Hume has made it impossible for us to experience what he would call philosophical relations, i.e., relations among physical objects. Since we cannot receive impressions of objects themselves, it follows that we cannot receive impressions of the relations that would occur among them either; if we are unable to perceive the relata of a relation (e.g., two or more physical objects), then that relation itself is also unknowable. Thus, the philosophical account of causality that Hume gives with definition (C1) is not a true account of causation, as it cannot fit in with his grand science of Human Nature, a science which only includes within itself that which can be accurately known and is relevant to human beings. Only if Hume were to accept the causal realist position, thereby accepting the existence of objective relations supported by secret causal powers, could he claim the philosophical definition of the causal relation to be a legitimate definition. As it stands, however, I have proven in the second major section of this paper that Hume is best interpreted as being a casual anti-realist, as being of the opinion that the power and efficacy of causes lies wholly in the human mind. Consequently, Hume cannot say, on pain of contradicting his entire theory of Page | 22 ideas, that the philosophical definition of causality is able to be understood by us, i.e., he cannot say that we actually receive an impression of this relation of two or more physical objects. Objects and any relations that would form among them are, under Hume's system, not able to be discovered through one's perceptual faculties. The vulgar or common man may be able to believe in philosophical relations, but they cannot experience/know them. So why does Hume even bother to mention his philosophical account of causality if he claims we can never experience objective cause and effect relations among objects? I think the reason why Hume gives us two definitions of cause, including the philosophical definition, is because he wants to capture as much of the essence of causation as possible; he wants to report in his Treatise all of the different possible ways that the cause and effect relation can be conceived by us. The vulgar have their way of viewing the cause and effect relation, as a philosophical relation, and the wise (no doubt including Hume!) have their way of viewing the cause and effect relation, as a natural relation. Hume holds himself back from saying that the vulgar or common conception of causation is outright wrong and a nonstarter, but that does not stop him from pointing out the irrational ground on which the vulgar base this conception of causality; from an empiricist standpoint, which is the standpoint Hume is following, one cannot come to possess knowledge of an objective necessity out there in nature. All that said, the majority of human beings still view objects themselves as the true bearers of causal efficacy or power. To account for this almost universal belief, Hume wanted to make a reference to the common view of causality in the Treatise. He does not agree with this view, but it is nevertheless what many people believe to be the essence of causality; thus, Hume probably felt obligated to mention it and show the limits to such a definition of the cause and effect relation. Hume leaves open the possibility that the vulgar may actually be right in their positing Page | 23 an intrinsic causal structure to nature, yet such a claim cannot be validated or disproved by appealing to experience or reasoning concerning matters of fact. So, by process of elimination, Hume is left with his second, natural definition of the cause and effect relation (C2). It is clear that Hume is dissatisfied with this definition as well; this has already been well-documented in the text and in the secondary literature. Even so, I believe he thinks of (C2) as capturing more of the true essence of causality than (C1), because of the causal anti-realist position he supports throughout both the Treatise and Enquiry. For Hume, the cause and effect relations that exist for us are only present in the mind; they are perceptions of impressions causing ideas, ideas causing other ideas, etc. Any other cause and effect relations that we posit, like those between physical objects, are beyond the scope of human understanding and empirical observation. Hence, they mean nothing to us and are irrelevant. Hume was so unambiguous and clear on this point that it was at first odd to us why defenders of the New Hume would even attempt to mount an attack on the traditional, anti-realist reading of Hume. Hume claims: "necessity is something, that exists in the mind, not in objects" (THN 1.3.14.22). It is rare for any philosopher to be so clear on a point such as this! Consequently, based on Hume's being an anti-realist, who believes causality to be a mental phenomenon and not an external one, we may conclude that definition (C2) is the winner and thereby captures the essential characteristic of causation. Cause and effect relations are solely determinations of the mind to move from one idea/impression to the idea of its usual attendant. Now that I have proven Hume only endorses one of his two definitions of the cause and effect relation, namely, the natural definition, we must ask: Is there still a dispute? I would say no, since there is no longer anything to argue about. In showing that these two definitions are not dueling definitions battling for the same top spot as best definition of cause, I have taken Page | 24 away the major issue dividing scholars. The only feasible definition of cause that actually dovetails within Hume's anthropocentric (human-centered) philosophy is definition (C2), which emphasizes the human mind's role in the experience of cause and effect relations. Definition (C1) cannot be embraced by Hume as a legitimate definition of cause, because it goes against everything that he had worked for in his theory of ideas. According to Hume, we cannot be certain of the existence of an external world, we cannot be certain of the existence of physical objects, we cannot be certain that there actually exists an objective necessity in nature, and so on. But since definition (C1) presupposes the existence of objects (which Hume does not allow), it follows that Hume would never seriously accept such a definition of the cause and effect relation. Thus, there is no longer any 'two definitions of cause dispute.' V. Conclusion In conclusion, this paper began by asking the question: Is Hume a causal realist? It was my claim that if we were able to get a definite answer to this question, then we would be able to solve, or at least partially solve, the two definitions of cause dispute. In my attempt to answer the first and major question of this paper, Is Hume a causal realist?, I noted the difference between two major groups of interpreters: (1) Those scholars who interpret Hume as a causal anti-realist and (2) those scholars who interpret Hume as a causal realist. The former are defenders of the "Old Hume," while the latter are the supporters of the "New Hume." I have argued throughout this paper that there is an overwhelming amount of evidence that should lead us to read Hume as a casual anti-realist, one who believes that cause and effect relations are felt and known in the mind of the perceiver alone; not in objects themselves. There is a staggering amount of textual evidence to back up a causal anti-realist reading of Hume, but that is not the only major piece of evidence to which we need turn; when we attempt to interpret Hume in one Page | 25 of these two ways, we must also think about what account of causation makes sense for Hume to endorse, given his entire project to create a science of human nature. Hume's philosophy is, as we know, human-centered; and his views on causality are no different. According to Hume, the cause and effect relations that can exist for us are supported by our minds. In multiple places, Hume specifically rejects that physical objects themselves, the Deity, or some combination of these two principles could be responsible for upholding the causal relations among ideas and impressions. Whatever necessity (or cause and effect relation) we can experience can only exist in the human mind. Put briefly, the causal order of nature that we perceive is based in Human Nature. It almost goes without saying that this was quite a Copernican Revolution in thought: placing Human Nature, and, specifically, the human mind as the support of causal relations, instead of objects, must have seemed utterly extravagant and ridiculous to those of his day. The New Humeans, of course, were not without a response to my interpretation of Hume. One will remember that the defenders of the new Hume argued that their causal realist reading of Hume was also backed up with textual evidence (THN 1.3.14.27). I have shown, however, that the scant textual evidence they do give is nowhere near sufficient to provide support for a causal realist interpretation of Hume; in fact, all of the passages that they can offer to support their reading at best show that Hume was an agnostic when it came to the existence of an objective necessity that existed in nature. Even their strongest argument-that belief in objective causal relations among physical objects is a naturally inevitable belief-is riddled with problems. On the whole, therefore, I came to the conclusion that Hume is best interpreted as being a causal anti-realist. Having a clear answer to the major interpretative question of this paper, I was then able to settle the 'two definitions of cause dispute' that arose when Hume gave us not one, but two, Page | 26 definitions of the cause and effect relation. The 'two definitions of cause dispute,' I think, centers around the faulty belief that Hume took both of his definitions of cause as equal, or nearequal , contenders for the right of being called the 'number one' definition of cause. But there is simply no textual evidence to suggest this equivalence; in fact, it is quite the contrary. For Hume, only one of these two definitions truly merited being called a definition of the cause and effect relation. Given his overall empiricist standpoint, his theory of ideas, his 'Copy Principle,' and his focus on Human Nature, Hume could only plausibly choose the definition of the cause and effect relation as a natural relation (C2). The other philosophical definition of cause (C1), so I argued, was only mentioned by Hume to report the way the common or vulgar man viewed the cause and effect relation as a relation among physical objects. Hume is clear that we can only receive an impression of necessity in our minds; there is no way for us to perceive philosophical relations among objects, because objects are unknowable things. As Hume is left with only one definition of cause, the great dispute appears to be settled. Page | 27 Bibliography Broughton, Janet. "Hume's Ideas about Necessary Connection." Hume Studies, Vol. 13. (1987). Pp. 217-244. Costa, Michael J. "Hume and Causal Realism." Australasian Journal of Philosophy, Vol. 67, No. 2 (1989). Pp. 172-190. Costa, Michael J. 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