Michael Morales 93 STROUD'S HUMEAN SKEPTICISM Michael Morales Penultimate draft for publication in Southwest Philosophical Studies, Vol. 32, Spring 2010, p. 93-97 I. Introduction In "The Constraints of Hume's Naturalism,"1 Barry Stroud takes on the task of looking at Hume's negative and positive accounts of induction in conjunction. Stroud goes about doing this so that we might walk away with "a more general lesson about naturalism, at least when it is indulged in for philosophical purposes" (343, Emphasis added). Initially, we are wont to ask: what kind of naturalism does Stroud believe Hume to be investigating? As Hume's titles to the Treatise and Enquiry suggest, he is seeking a justified explanation to human nature and/or understanding which seems to be grounded in inductive inference (explicated in Section II). In other words, Hume is trying to find a way around the problem of induction in regard to human nature without recourse to talk of perceptions and senses (Section III). Given the boldness of Stroud's quote from above, there should be some explicit talk of this general lesson about naturalism outside of Hume's, but there is none that is readily apparent. If a more general and philosophically motivated lesson about naturalism is to be gleaned from Stroud's investigation of Hume, then we should take this to be a lesson implicit in Stroud and not Hume. Hence I shall argue that Stroud tacitly endorses the skeptical conclusions of David Hume about naturalism in general when indulged for philosophical purposes (Section IV). II. Naturalism, Induction, and Skepticism To understand Stroud's critique of Hume, we need to show how the terms "naturalism," "induction," and "skepticism" are being used in Hume. Hence we must first acknowledge that naturalism is the overarching principle that becomes illuminated by what is called the problem of induction and the so-called skepticism that Hume reached because of this problem. Furthermore, all of these terms have consequences in epistemology, the area of philosophy concerned with knowledge. Very succinctly, questions of epistemology are those that are concerned with how we acquire and arrive at beliefs that count as knowledge. Hence it will be necessary to first explicate Hume's problem of induction and the conclusion that his opponents have called skeptical. From there we should be able to see the naturalism that Hume endorses. Broadly speaking, induction is the process of arriving at a general conclusion from particular instances. The problem of induction in Humean terms2 is laid out as follows. First there are two kinds of propositions, "Relations of Ideas" (RoI) and "Matters of Fact" (MoF). Here is how we distinguish between these two kinds of propositions. RoIs are discoverable by mere creations of thought. For example, the proposition "2 + 2 = 4" expresses a truth and our knowledge of this truth is expressed in a belief that was attained by merely thinking about the abstract process which produces the conclusion that when we add "2" and "2" together we get '4." RoIs also have the characteristic of being as such that when one expresses their contrary it implies a contradiction, e.g., "2 2 = 4" is a Stroud's Humean Skepticism 94 contradiction. MoFs are those propositions that are found to be true by empirical research and whose contrary does not imply a contradiction. For example, we have the MoF that "All dogs are fat," The contrary MoF "All dogs are skinny" does not imply a contradiction. To discover whether these MoFs are true or not, we go out and look at the world to see if all dogs are fat or skinny. In other words, the knowledge of MoFs comes from the world itself. Secondly, for every proposition Hume considers he asks whether it is a RoI or a MoF. If the proposition is a RoI, then no empirical research is necessary. If it is a MoF, then we need to do some empirical research. A good way to exemplify this is through the argument, Premise (1): In the past the sun has risen. Conclusion: Therefore, the sun will rise tomorrow. The contrary proposition of Premise (1), i.e., "In the past the sun has not risen," does not imply a contradiction since part of our empirical research involves looking at a part of the world where the sun has not risen in the past, say, the Antarctic. However, since we are not in the Antarctic, we can localize Premise (1) for our purposes to a part of the world where in the past the sun has risen. To reach our conclusion, though, requires an implicit proposition. Let's call it Premise (1a) which says, "The future will resemble the past." When we put it into our argument it looks like this: Premise (1): In the past the sun has risen. Premise (1a): The future will resemble the past. Conclusion: Therefore, the sun will rise tomorrow. And this paints the picture of how we arrive at our understanding of the world through inductive inference, but how is this a problem and for whom is it a problem? It is a problem because we have knowledge of the past, but we have no knowledge whatsoever of what the future is like. Hume says that we reach our conclusions about MoFs through habit with the assumptions or expectations we make like those in Premise (1a). Saying that our knowledge of the world is acquired through habit is a problem for those of Hume's time because they maintained that our knowledge of the world, that the future will be like the past, that objects persist in their continued existence when not being perceived, that there is cause and effect, and that there is uniformity in nature were founded on reason or something like RoIs (Cf. John Locke's An Essay Concerning Human Understanding"). Furthermore, this is problem because all data and "knowledge" of the sciences, and of every human, is acquired in this way, which implies that science and human knowledge is not rational. Also, saying that our knowledge of the world is habitual puts humans on par with animals since animals display these inductive capabilities which is also a problem for philosophers like Locke who maintained that our rational capabilities set us apart and placed us above all creatures of the world. Hence Hume encourages us to give up normative epistemology which says roughly that our knowledge of the world ought to come to us through reason. When Hume follows induction to its philosophical end, he finds that it leads to an even more radical conclusion, that of skepticism, which is as follows: If reason does not justify our knowledge and understanding of the world, then we acquire our knowledge of the world exclusively through our sense perceptions. If we acquire our knowledge of the world exclusively through our sense perceptions, then we can only have knowledge of Michael Morales 95 those sense perceptions and only those perceptions. Therefore, we have no knowledge whatsoever of the external world, but of sense perceptions. What we are skeptical of, then, is that there is even an external world to be known or from which to gain knowledge. We are now to in position to see where Hume's naturalism comes into the picture. Seeing that we are to give up on reason providing us with knowledge of the world, Hume says that the positive outcome of gaining knowledge of the world through habit is that it is perfectly natural for us to do so. If this is perfectly natural, then we can explicate MoFs, and hence the world, without having to make questionable metaphysical claims that an entity like God gives us the guarantee that we can be certain that our inductive inferences made from our sense perceptions give us knowledge of the external world. Bringing God or some other entity into the picture is to appeal to something that we cannot confirm by empirical research. III. Can Hume Get Past Induction Naturalistically? Barry Stroud introduces Kemp Smith's work for the purpose of showing that Smith was perhaps the first to espouse the thesis that Hume's naturalism could not be understood without his skeptical considerations (342). Rather, the idea is that Hume only reached his negative, skeptical conclusion to show that if a rigorous philosophical inquiry of induction reveals that "reason" does not justify one's beliefs pertaining to the external world, then our beliefs must be justified naturalistically, i.e., explain mental phenomena as it is in nature without having to make any epistemic leaps of faith or positing a bloated ontology. Hence Hume wanted to reveal the weakness in Locke and other others who shared the belief that reason justified our experience and knowledge, especially since reason was thought to distinguish humans over and above all in the animal world (340). For this reason Stroud's project comes in two parts. The first part consists in showing why Hume seeks a naturalistic explanation of human nature. Just as a student of animal nature will go out and observe how animals behave in their natural surroundings and record the findings, so too will a student of human nature go about studying other humans. Hume was well aware that the study of human nature in this way involved inductive inference. So, if any philosophical inquiry of human nature involved inductive inference, then the first constraint of Hume's naturalism is the problem of induction, which means that the burden falls on Hume to show how induction is to be justified and explained. This first part of Stroud's project shows that Hume's naturalism (his positive account), then, consists in providing an account of human nature without appealing to induction, or as Stroud illuminates, "To put it in crude terms, it is a question of how human beings get, or what takes them, from input to output" (343). At this point Stroud shows that Hume's detailed account begins with our initial, fleeting impressions, and then through other principles "the mind slides easily along a certain series of perceptions" treating our inductive beliefs as a "kind of fiction." Ultimately, Stroud says that Hume hoped that these principles would be as such that "human beings with such limited experiences will universally and inevitably come to believe." Furthermore, Hume gives us this account without any appeal "to the existence of. . . independently existing objects" (345). Hume thought that a combination of these Stroud's Humean Skepticism 96 principles and nature would provide the justification for explaining how a student of human nature uses inductive inference. What this does instead is provide another constraint for Hume, which brings us to the second part of Stroud's project. The second part is to use Hume's "special embarrassments and dissatisfactions" to bring to light a lesson about Hume's naturalism and naturalism in general (343). Since Hume's account of the principles of the imagination were given without appeal to the existence of the external world, and since he claims the mind treats the external world as a fiction, experience has the consequence of being purely psychological, totally removed from nature. Thus, Stroud says, Hume's account stands outside of nature so completely that it fails to be both naturalistic and explanatory. This means that Hume's skeptical considerations are so strong that in trying to evade them his account of how the naturalist accounts for her beliefs is outside of the naturalist and even the rest of the world, especially since all perceptions are fictions (346). The lesson is this. Hume's naturalism is not natural in the least. IV. Stroud's Silent Skepticism However, Stroud also claims that the constraints of Hume's naturalism will shed some light on the constraints of a naturalistic, philosophical inquiry of human nature in general. If we are to understand Stroud correctly, then Hume provided us with his skeptical argument for one reason. The reason is this: Once we push our philosophical investigations to their logical conclusions, we will be provided with the basis from which to begin a naturalistic account of the external world and the human mind, but the basis is shaky. Stroud shows that Hume's naturalistic account for the persisting existence of the world and of human activity seems to exclude nature and is hence purely psychological. And if this is the case, then what Stroud has done was to show, by way of transitive property, that in spite of Hume's own efforts, we can only reach the level of skepticism when regarding our epistemological beliefs about the external world and any attempts at explaining human understanding and the world naturalistically. Finding universal principles of the mind and/or imagination are virtually impossible since the student of human nature can only appeal to a deficient source of input that is heavily reliant on experience, which Stroud calls "the poverty of the input." An obvious objection would be that Stroud is speaking of Hume's naturalism exclusively and that I have no proof to raise such a conclusion. Since I maintain that Stroud is implicitly supporting a skeptical claim about naturalism in general, we must turn to Stroud's own words. First, of inductive inference Stroud says that Hume's project "is a completely general account of virtually all human belief in anything at all" (348). This point is perhaps better illustrated when Stroud says: What is true of the naturalistic study of both animals and human beings. . . is carried out in each case by human beings. That presents no difficulty. . . for whatever we find to be true of animals. But when human beings are both agents and objects of naturalistic study, what is found to be true of the objects studied must somehow also be understood to be true of those of us who conduct the study (348). Michael Morales 97 Here Stroud is laying down the framework for what a general naturalistic study of human and animal nature amounts to and what it is true of. Rightly, a naturalist would reject Hume's naturalism, as Stroud points out. They would indulge in their inductive inference and carry on with their lives. However, we must remember that these skeptical worries only surface when "indulged for philosophical purposes." This means that if we attempt to arrive at justifying naturalism in general philosophically, then we will inevitably meet a skeptical end. This is especially true since a naturalistic account of anything must invariably make reference to nature in order to have explanatory force or value. In other words, Stroud implicitly endorses the thesis that it is impossible for philosophers to give a justified naturalistic account of anything since justification is supposed to be justified by reason and so non-circular. The evidence that Stroud is speaking to philosophers exclusively comes from a parallel that he makes with Hume. Where Hume feels "philosophical melancholy and delirium" nature alleviates him from his skeptical worries and so he is able to dine, play a game of backgammon, and be merry with friends; we can do the same, and the "we" here changes context as Stroud's parallel shows. The "we" Stroud is referring to are philosophers, for philosophers are the only ones who ultimately seek justification "in the right way" (350). The right way entails non-circular explanations. The philosopher, with all of her reductionist tendencies, seeks to avoid circularity. Any non-circular explanation of human nature would require that there be no reference to nature in thought, belief, or action. However, Stroud says that any "rich conception of nature. . . at least in general terms" should include "the whole world of enduring bodies in space and human bodies and human actions in interaction with them and with one another" (350). In a word, he is talking about empirical evidence. Furthermore, naturalism in general, and in the sense that a great many of us think of it today, is one where our explication and understanding of the world is completely consistent with the findings of science. Science proceeds from empirical evidence. Empirical evidence is rife with inductive inference, but it matters not to science if explanations deriving from empirical evidence are circular. Such evidence will suffice as a justified explanation, as knowledge. The implication is that philosophers are not able to provide such a naturalistic conception given their reductionist approach. Thus Hume's skeptical considerations are always the undercurrent to any philosophically rigorous, naturalistic inquiry. V. Conclusion and Commentary Since Stroud's project is to shed light on the general lesson about a philosophical investigation of naturalism through Hume, then it can be inferred that Stroud has reintroduced the skeptical interpretation of Hume as conclusive as it pertains to philosophers only. Therefore, we can conclude that Stroud has effectively shown that any philosophically rigorous general account of naturalism about the external world is ultimately not justified since we will help ourselves to inductive inference without fail. In other words we are advised to look at Hume's skeptical argument in conjunction with his naturalistic account only to see that any philosophical attempt at naturalism in general is still ultimately impossible, though Stroud chooses to remain evasively silent on the issue. Stroud's Humean Skepticism 98 NOTES 1. In Synthese (2006) 152:339–351. 2. As is evidenced by his account in Treatise of Human Nature.