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Rollag 1/12 5/15/10 From Descartes to Hume: The Influence of Reason on Causation and Free Will Introduction After Hume published his Treatise, in 1739-40, John Stewart attacked him for advancing the position “that something may begin to exist, or start into being, without a cause.” Hume, in a letter dated February 1754, flatly denies that he ever “asserted so absurd a Proposition as that any thing might arise without a Cause.” Hume says, “I only maintain’d, that our Certainty of the Falsehood of that Proposition proceeded neither from Intuition nor Demonstration, but from another source.” In this letter, Hume is flustered by the fact that Stewart misunderstood his philosophical purpose and conclusion, which leads Hume to disavow the Treatise for his later work, Enquiries Concerning Human Understanding (Hume’s Letters, 187). In this paper, I argue that it is easy to misunderstand Hume’s conclusions and philosophical purpose of the Treatise given the traditional mentality in philosophy. Since Descartes put in motion the traditional mentality, I explain Descartes’ philosophical motivations and conclusions regarding causation. Since Descartes’ philosophy was in reaction to the increase in scientific discoveries during his lifetime, Descartes’ philosophy emphasizes the use of reason. Like the scientist he was, Descartes has a philosophical point of view that he can discover, through reason, objective truths about the external world. I explain that Descartes uses reason to prove with certainty that he exists, and he and everything else in the external world depends on God’s existence. Then I present Elizabeth’s objection that these conclusions are incompatible with free will, and I offer Descartes’ argument for their compatibility. Following this, I resolve another apparent problem for free will in Descartes’ philosophy, that we are the freest, and virtuous, when we do what reason dictates. The Cartesian tradition, and society’s heavy reliance on science, makes it is easy to

Rollag 2/12 5/15/10 mistake the focus of Hume’s Treatise and misinterpret his philosophical conclusions. I explain that as a reaction to Descartes’ philosophical reaction to science, Hume’s philosophy focuses on epistemological concerns about the capabilities of human knowledge. I show that Hume denies that Descartes’ account of causation is proved through reason, and instead affirms that causation is simply a principle of our mind to associate ideas. As a result, I explain that Hume’s account of free will is not in need of a defense of why it is incompatible with his account of causation. I also show that Hume argues against reason being the sole foundation for moral action. In effect, Hume’s Treatise is a rebellion of the traditional mentality, set by Descartes, and works to reorient our perspective on how we know what we know, especially with regard to science, which is easily lost on someone, like Stewart, who cannot escape the traditional mentality. Following this, I offer a resolution between Descartes and Hume’s philosophy in a summary of what I have covered. Descartes’ Philosophy Descartes’ philosophy was influenced by the increase in scientific discoveries during his lifetime (1596 – 1650). As a mathematician, physicist, and biologist, Descartes admired how reason enabled one to prove without a doubt the certainty of its conclusions (Vol. I, 114). Descartes understood how easy it is to error in forming one’s beliefs (Vol. I, 112), and as a philosopher, Descartes shows that our knowledge of the world can be grounded in the certainty that reason provides (Vol. I, 112 & 120). In his Discourse on Method (1637), he shows how one can use reason correctly to conclude indubitable truths in metaphysics (Vol. I, 112 & 120). Through reason, Descartes proves with certainty that he exists (Vol. 1, 127), God exists, and he and everything else, depend on God’s existence (Vol. I, 128 – 129). These arguments might have been a small amelioration of religious fears of science during that time. Descartes’

Rollag 3/12 5/15/10 enthusiasm for reason and science leads him to have a metaphysical viewpoint that he can discover objective truths about the external world, independent of himself. Descartes’ method and metaphysical outlook sets the tradition for future philosophers and scientists. Descartes and Causation Descartes wanted to rebuild his knowledge of the world from secure foundations up (Vol. I, 117, 120 & 122). After he doubts everything except some few rules about how to live well, Descartes discovers his first indubitable truth that he is a thinking thing that exists (Vol. I, 127). His second indubitable truth, God’s existence, substantiates the certainty by which he knows that he is a thinking thing that exists and that he knows that the external world exists (Vol. I, 127 – 141). God’s existence is proved by the principle of the necessity of causation; in other words, it is contradictory for something to come from nothing (Vol. I, 128). Since Descartes has doubts, he notices that he is not perfect (Vol. I, 126). Since he is not perfect, he has the idea of something more perfect than himself (Vol. I, 127). Since an idea cannot come from nothing, and the idea of something more perfect than himself cannot come from himself, something less perfect, then it has to come from a being more perfect than himself (Vol. I, 128). Since Descartes recognizes that he has many imperfections, this being must have all the perfections that he and other imperfect things in the world lack (Vol. I, 128). Since it would be an imperfection not to exist, then an all perfect being must necessarily exist (Vol. I, 129). Thus, God, and all perfect being, necessarily exists, and everything else depends on his existence (Vol. I, 128 – 129). Elizabeth’s Concern for our Free Will Elizabeth questioned Descartes’ metaphysics; Descartes’ idea of causation appears incompatible with free will. Since everything depends on God, and God is eternal, infinite, independent, immutable, omniscient, and omnipotent (Vol. I, 128 – 129), how then can we be

Rollag 4/12 5/15/10 free? How can our actions be free if they depend on God? If our actions are not free, then how can our choices be free? Do our choices depend on God? Descartes argues that his idea of causation is compatible with free will. It is true that our actions depend on God, but the type of dependence needs to be clarified. God is the reason why we are actualized in the world. God actualizes everything that happens in the world, even our choices and our actions. However, God does not compel us to choose to do what we actually do. God, in his infinite knowledge, knows what we will choose to do and what we will do, and realizes our actions in the world in accordance with our choices. So, everything depends on God in so far as everything is real, exists, and occurs. This type of dependence is much different than a God that makes the world as he wants it to be. Though God does determine a standard for morality, God does not compel us in a manner in which we cannot but live up to this standard for morality. God endows us with a faculty of judgment, reason, but since we are limited beings, we do not always have all the information that would lead us to conclude what reason dictates (Vol. II, 39). So, while God wants us to judge correctly, in accordance with his standard for morality, God does not compel us to judge correctly; since we are not perfect, we are free to make mistakes (Vol. II, 39). But, God will be there to make sure that what we choose to do, whether it be what reason dictates or not, our choices and our actions will be actualized in the world. (Vol. III, 282)1. Descartes and Another Possible Problem for Free Will Descartes’ emphasis on reason also leads him to attribute morality and virtue to those who use their reason correctly (Kenny, 166). Since Descartes calls an action that is not controlled by a mind, a passion, and a passion that is controlled by a mind an action (Kenny, 177 – 178), 1

This citation refers to the whole paragraph. I didn’t want to put the same citation at the end of every sentence in this paragraph.

Rollag 5/12 5/15/10 then the right use of reason, to act, is to be in control of the passions. Descartes does not think that passions are bad (Kenny, 170). He thinks that since we have the ability to control them, we should not let them control our life (Kenny, 177). We are freest when we use our reason correctly because our faculty of judgment is our power or capacity for action, and when we do not use it, we are not free (Kenny, 168). True, it seems odd to say that doing what reason dictates is our greatest freedom because it seems to rule out our ability to choose what to do. But, in order to choose to do anything, to be free, we need a faculty of judgment, otherwise we would be compelled by passion. Reason is what sets humans apart from animals (Vol. I, 112). Humans have the capacity for virtuous action. All we have to do is use reason correctly. Since God determines the standards for morality or what we should do (Kenny, 189), and gave us a faculty to judge what we should do (Vol. II, 38), the correct use of reason enables one to know what to do (Kenny, 166). Although, we might not always know what to do given our limited knowledge (Kenny, 180). By doing what reason dictates, we feel pleasure in action (Kenny, 168 – 169) and we come to know what is virtuous (Kenny, 166). Hume’s Philosophy By understanding Descartes’ philosophical motivations, method, and conclusions, we are in a better position to understand why someone like Stewart could misunderstand Hume’s philosophical motivations, method, and conclusions2. Descartes set a philosophical tradition in which one’s philosophical frame of mind is like the frame of mind of a scientist. Like a scientist, Descartes places heavy emphasis on reason, and that one can discover objective truths about the external world independent of us. This mentality is pervasive and leads one, like Stewart, to misinterpret Hume’s arguments. Since science has only become more influential in our day to 2

Since many of Hume’s predecessors followed in Descartes’ tradition, such as Spinoza and Leibniz, understanding their metaphysical method and conclusions would also serve to elucidate Hume’s metaphysics.

Rollag 6/12 5/15/10 day life post Descartes’ lifetime, it is especially true today that it is hard to rid one’s self of this mentality to truly understand Hume’s philosophy and not to misapply it. In light of this, let me explain Hume’ philosophical motivations, method and conclusions regarding causation. Hume’s philosophy is a reaction to philosophers’, like Descartes’, reaction to science. While Descartes’ philosophy was an effort to found our metaphysical knowledge of the external world in certainty, Hume takes a step back and enquires from where we receive the certainty by which we have knowledge of the world (Treatise, Introduction). Hume says that before we begin to philosophize, we must first ground the terms that we employ in our reasoning (Treatise, 74-75 & 162). Hume agrees that reason is useful in deriving true conclusions, but Hume questions whether conclusions, like those of Descartes’, are derived from reason alone. In particular, Hume questions whether it is from reason that we receive the idea of the necessity of causation (Treatise, Part III). Since Hume thinks that all of our words are linked to our ideas (Treatise, 93 & 162), and all of our ideas are derived from impressions (Treatise, 72), he intends to discover the impressions that produce our ideas and fixes the meanings of our terms such as of the necessity of causation (Treatise, 74). Hume’s philosophy, as a reaction to Descartes’ philosophy and trust in science, becomes an epistemological inquiry into the nature and limitations of our knowledge as human beings. Hume’s philosophical viewpoint is that we need to investigate human nature, or our capacity for knowledge, before we do science or philosophize about the world (Treatise, 15 – 16). Hume and Causation Hume argues that philosophers, like Descartes, take for granted the principle that everything must necessarily be caused, instead of inquiring into the impression for which they received that idea. This leads them to fallibly conclude that a deity exists and moreover that we

Rollag 7/12 5/15/10 have innate ideas, both of which Hume blatantly rejects (Treatise, 160). There are two aspects of philosophers’, like Descartes’, belief that everything must have a cause. The first is that this is a principle that is an objective truth about the external world, independent of us. The second is that they think that they can prove through reason, either by means of intuition or by demonstration, the truth of this principle as an objective truth of the external world. Hume denies both of these aspects, and concludes that this principle is nothing more than a feature of our mind to associate ideas. Hume considers whether our idea of the necessity of causation could be fixed to impressions of features of the external world (Treatise, 75-80). Hume argues that in meeting these objects we neither intuit nor demonstrate that everything must have a cause (Treatise, 79). Hume has many arguments for this claim, but I like thinking about it in another way. If the idea of the necessity of causation arose from intuition, then we would be able to predict every effect that would occur by any object upon first sight of that object. We clearly cannot do this. Since we cannot predict what any object will do in its encountering another at first sight, then it is apparent that we do not observe any productive power that could be said to be had of objects. Since we do not observe any productive power in objects themselves, then it is neither absurd nor contradictory that an event could be uncaused. Since it is logically possible that an event could be uncaused, the necessity of causation is not demonstratively proved because in a demonstrative proof the opposite would entail a contradiction. Moreover, there is nothing that multiple instance of an observation of an event can prove anew of those events that intuition and demonstration could not prove in one instance (Treatise, 164). Thus, it is logically possible that events may be without a cause, and so our idea of the necessity of causation is neither received from intuition nor from demonstration, so it is not produced from reason, and it cannot conclude

Rollag 8/12 5/15/10 anything about features of the external world. So, when Descartes says that it is contradictory that something could come from nothing, Hume argues that it is not contradictory for an event to be uncaused and so something need not have come from anything. Hume proceeds to discover that our idea of the necessity of causation is derived from impressions that are produced within ourselves (Treatise, 165). In experiencing the world, we observe the constant conjunction of particular events following other particular events (Treatise, 165). In our mind’s reflection on experience, it becomes accustomed to associate acquired ideas of particular events with those of other particular events (Treatise, 165). It is pertinent that we experience more than one instance of conjoined events before we form the idea of the necessity of causation (Treatise, 164-165). To understand why this is so, it is helpful to consider why we think that say fire causes heat, but not that say my tapping my finger causes my bobble-head to wobble. The difference is in our experience of the uniformity of heat always following fire which is not experienced in the tapping of my finger and my bobble-head’s wobbling 3. By revealing that our idea of the necessity of causation is derived from impressions of reflection, we see that it only refers to our minds propensity to associate ideas (Treaties, 165). Hume and the Compatibility of Causation and Free Will Hume thinks that the need for freedom of the will falls from moral responsibility (Treatise, 407). We think that people should be morally responsible for their actions. If their actions are not free, then they cannot be said to be responsible for what they do. However, if our actions are not determined, and are merely the result of a randomness or chance in nature, then neither can a person be said to be morally responsible for what they do. Thus, Hume argues that our actions must be determined by our beliefs and desires. So, Descartes and Hume agree that 3

It is interesting to note that if my tapping of my finger was always followed by my bobblehead’s wobbling, I may be inclined to think that tapping my finger caused my bobble-head to wobble.

Rollag 9/12 5/15/10 our actions must be determined and not independent of a cause. Hume’s account of necessity is a propensity of our mind to associate ideas. Since this is all we can know about necessity, then our actions being determined by our beliefs and desires is simply our minds’ association our ideas of our actions with our beliefs and desires (Treatise, 407). This is a very minimalist account of how our actions must be determined because it only offers an explanation of what we can know about necessity and volition. Hume’s metaphysical account of the world does not involve an objective principle about the reality of the world that events must be caused. Also, Hume does not stipulate an omniscient and omnipotent God that everything in the world depends on. As a result, Hume’s account of necessity is not in need of a defense of why it is not incompatible with free will. Given a science-like frame of mind, one could easily misunderstand Hume’s account of necessity and volition as an objective account of the reality of their compatibility, and not an explanatory account of their compatibility. But, Hume stresses that it does not make sense to speak of an objective account of necessity independent of a human’s perspective; so, he is offering a more epistemologically correct account of necessity, volition, and their compatibility. Since Hume’s compatibilism does not refer to an objective account of the reality of the external world, it cannot be used in defense of free will and determinism in the contemporary debate. Hume also rejects philosophers’ like Descartes’ accounts of moral actions as produced from reason alone. Descartes thought that it is the right use of reason that we are moral. Hume emphasizes that moral actions are not founded in reason; they are not devoid of sentiment (Enquiries, 170-175). Hume thinks that we are essentially sentimental creatures, and this drives us towards action. Since Hume brings morality back down to the level of sentiment, away from the ideal of reason, Hume makes moral actions more accessible to humans. Moreover, since

Rollag 10/12 5/15/10 morality is not held to the standard set by some all perfect being, then it is easier for us to be able to understand what is and what is not moral. However, Descartes did allow that we know virtuous acts through how they affect our passions (Kenny, 168-169); if something is pleasurable, then through reason we can decide whether it is a virtuous action. While Hume thinks that sentiment is necessary for virtue, Descartes does not deny this. Also, while Hume emphasizes that sentiment is necessary, Hume does not rule out that reason is also necessary. So, both Hume and Descartes could agree on what moral actions are, even though each would emphasize a distinct aspect of what characterizes them. A Resolution It is easy to misinterpret Hume’s arguments if one is stuck in Descartes’ science-like frame of mind. Like Stewart, one can be distracted by Hume’s negative account of causation and not realize his overarching conclusion that the certainty by which we know that an event must be caused, or the certainty by which we know the founding principle of science, is by means of our minds’ propensity to associate ideas. One might also be tempted to think that Hume’s account of necessity and volition provides a new form of compatibilism that can be used in the contemporary debate of free will and determinism. But, this would be a misapplication of Hume’s philosophy; Hume’s compatibilism is only in terms of what we can know and not in terms of an objective feature of the external world. Hume’s philosophy is a rebellion against the traditional mentality in philosophy, like Descartes’, and works to reorient our perspective on our capacity for knowledge. His philosophy shows that philosophers in line with the Cartesian tradition need to be more modest in their assertions of the capabilities of reason. But, since Descartes lived during the peak of the scientific revolution, against a background of a dogmatic mentality towards knowledge, we can see why Descartes would have

Rollag 11/12 5/15/10 more rashly than not thrown the use of reason around. Descartes was excited that there was a criterion for knowledge, reason, and that everyone had the capacity to use it. Moreover, since science works so well, we can forgive Descartes for heavily relying on its founding principle that everything must be caused in order to conclude metaphysical truths about the world. Since our society has only become more dependent on science, it is even more difficult today to reorient our perspective on knowledge the way that Hume wants us to. So it is important to keep in mind that Hume’s philosophy is a reaction to philosophers’, like Descartes’ reaction to science, as an epistemological inquiry of the capabilities of our knowledge. This allows one to understand that Hume has a more epistemologically correct account of causation, which is not in need of suave maneuvers to defend its compatibility with free will, in contrast to those in line with the Cartesian tradition.


Descartes, Rene. The Philosophical Writings of Descartes (Volumes 1 & 3 (Paperback)). New York: Cambridge UP, 1991. Print.

Rollag 12/12 5/15/10 Descartes, Rene. Descartes Philosophical Letters. Translated by Anthony Kenny. Minneapolis: University of Minnesota Press, 1981. Print. Hume, David, and J. Y. T. Greig. The Letters of David Hume. Vol. 1. Oxford: Clarendon, 1932. Print. Hume, David, L. A. Selby-Bigge, and P. H. Nidditch. A Treatise of Human Nature. Second ed. Oxford: Clarendon, 1978. Print. Hume, David, and L. A. Selby-Bigge. Enquiries Concerning Human Understanding and Concerning the Principles of Morals. Third ed. Oxford: Clarendon, 2008. Print.

Misunderstanding Hume  
Misunderstanding Hume  

How it is easy to misunderstand Hume's analysis of determinism, and consequentually his positive account of free will.