David Hume, one of the foremost philosophers of the 18th century, was a skeptic and empiricist whose outlook on free will is based heavily in the sciences and what is known. Hume, being a compatibilist, deals mainly with the concept of reconciling the freedom and emotional nature of humanity with the coldly rational perspective of determinism. According to Hume, human behavior is commanded primarily by desire, instead of reason - "reason is, and ought only to be the slave of the passions" (Hume, Treatise, p. 295). The concept of free will is summarized greatly through the differentiation between liberty and necessity; the things that we need are not necessarily the same as the things that we want. That being said, Hume eschews the notion that "thought is more active than matter," and that many of our actions come as the result of necessity (Treatise, p. 249). In his mind, there is no difference between moral and physical necessity - biological needs and ethical values are one and the same; any difference is "without any foundation in nature" (Treatise, p. 171).
According to Hume's compatibilist position, there are several conclusions that deal with the subject of liberty. First, actions that are taken by the individual by our own volition are moral or good; immoral actions that we take are those influenced by an external agent; actions spontaneously taken are good. Next, morality is impossible if liberty negates necessity; for an action to be moral, it must be freely taken, not just necessary. Essentially, free actions stem directly from the desires of the agent, giving them responsibility for their actions. If something is done without their will or desire, it is the result of someone else's coercion. There is still a cause for the action, it just does not come from the agent. As a result, moral responsibility must only be expected for those individuals whose behavior is caused, or necessitated:
"Actions are, by their very nature, temporary and perishing; and where they proceed not from some cause in the character and disposition of the person who performed them, they can neither redound to his honour, if good; nor infamy, if evil" (Hume, Enquiry, p. 161).
Hume's is a causal deterministic point of view; he states that liberty and necessity go hand in hand in deciding the eventual actions of a human being. Hume defines free will as 'liberty,' stating that to be "a power of acting or not acting, according to the determinations of the will" (Hume, Enquiry, p. 159). Necessity, on the other hand, is what Hume uses to represent determinism: "the uniformity, observable in the operations of nature; where similar objects are constantly conjoined together" (Hume, Enquiry, p. 149).
Equating determinism to divine will, Hume is extremely critical of the thought of God as the ultimate creator and determiner of good and evil. To his mind, this removes accountability for criminal actions on the individual; what's more, he states that God's position as "perfect" would be called into question, as he is the one who can be attributed to the apparent existence of evil in the world. As a result, Hume dismisses the thought of pure determinism as a measure of spiritual fate (Enquiry, p. 101).
Hume's also philosophy contains a firm disbelief in synthetic a priori knowledge - he believes that there is no way of knowing how people will react to certain situations, because they have not been experienced. According to Hume, our knowledge is restricted to our experiences; therefore, we cannot predict or determine the outcome of something we have not gone through ourselves. While we can imagine possible outcomes, there is no true knowledge that can be gleaned from something that we have no experience of. Hume states that "experience and observation" are our only foundations for making a logical argument (Hume, Treatise, p. 7).
One significant problem with this attitude of free will is that it can be used to absolve someone of hurtful or negative actions. For example, if someone was told or forced by an external agent to murder someone, would it truly be their fault? According to Hume's philosophy, it would not, and therefore they should not shoulder the responsibility. However, they are still the physical agent by which the violent act was done, and so some feel that the responsibility should be theirs. What's more, there are those who believe that determinism or free will, as concepts, do not define our morality; instead, morality is just defined by irrational human sentiments that are independent of theses like these.
Hume believes that determinism indeed exists; however, free will must be able to work within determinism as well, making the two concepts compatible. On the subject of the aforementioned dilemma - that of holding someone responsible for the external agents that drive them to do things - it should be stated that only a human being possesses the ability to carry extremes of emotion, such as approval or disapproval, which are the indirect, lesser permutations of love and hatred, respectively (Hume, p. 331). It all relates directly to Hume's "dilemma of determinism," which states that actions occur either out of complete randomness or causal determination (Blackburn, 1996). Regardless of the choice made by the individual, the responsibility does not fall upon said individual.
With David Hume, actions and responsibility are never strictly a case of the problem of free will; when there is a durable quality of mind, or a character trait that is consistent with the person, then there is a case for responsibility for their actions. Crimes of passion, on the other hand, do not hold the person responsible, as those are unusual circumstances. In the earlier example, someone murders someone else because of external agents, like the loss of a job or the discovery of infidelity - this would not make the person responsible, as they are not a serial killer, nor were they prone to murder as an aspect of their character. If they had the feelings and desires to kill that person beforehand, they can be held responsible for those, despite them not being showcased in their acts. For Hume, what is inside the mind can be held accountable; the physical action, however, is subject to external agency, and can be blamed on other factors.
References
Blackburn, Simon. (1996). 'Hume's Fork.' Oxford Dictionary of Philosophy. Oxford University
Press.
Hume, D. (1777). Inquiries concerning Human Understanding and concerning the Principles of
Morals Third Edition,. L. A. Selby-Bigge (ed.), Clarendon Press, Oxford.
Hume, D. (2003). A Treatise of Human Nature. New York: Dover.
