In these chapters, Hume defends a compatibilist account of free will. This holds that we can be responsible for our actions even if they are caused by forces that are out of our control.
One thing to pay particular attention to is Hume’s claim that we we hold people responsible only for the things they do that are consistent with their character (2.3.2, par. 6). That is an important element of both his version of compatibilism and his moral theory.
There are two chapters, “Of Liberty and Necessity” and the imaginatively named “The Same Subject Continued.”
In “Of Liberty and Necessity,” Hume begins by defining the term “will” as “the internal impression we feel and are conscious of, when we knowingly give rise to any new motion of our body, or new perception of our mind” (2.3.1 par. 2). The will, in other words, is a feeling. It is caused by feelings of pleasure or pain. And it is felt only when we “knowingly give rise to any new motion” of our bodies; as I understand it, that is equivalent to intentionally moving our bodies. You have the relevant feeling when you intentionally kick a ball and you do not have the feeling when your leg jerks out because a doctor taps your knee.
He then states what he takes to be the disagreement about free will. He asserts that the participants on both sides of the argument agree that physical things (“external bodies,” meaning bodies outside the mind) move because they are caused to move by other physical things. Since a cause makes its effect happen, the movements of physical objects are “necessitated” and they have no liberty to move in ways that are contrary to how they are caused to move (2.3.1 par. 3). What is in dispute is whether the mind is similar to the physical world. Suppose my mind changes from the state of not having the will to get a drink of water to having the will to get a drink of water; in other words, I decide to get a drink of water. Is that change caused in the same way that changes in the physical world are caused or not? The answer to that question is what the two sides disagree about.
Hume gives a brief statement of his theory of causal relations. First, causes are uniform: the same kind of cause always produces the same kind of effect. Second, the constant union or “conjunction” of a kind of cause and its effects leads us to infer that the cause made the effect happen. The bulk of the first chapter is split between these two points.
First, he tries to show that human behavior is uniform: the same kinds of motivations lead to the same kinds of actions. This is the task of paragraphs 5-13. This will be our first major topic of discussion: is human behavior uniform in the way Hume’s argument requires?
Second, he argues that the inferences we make about human behavior are causal inferences. Roughly, the only way we can make sense of human behavior is by treating it as being caused. This is what he tries to show in paragraphs 14-17.
The second chapter, “The Same Subject Continued,” begins with three reasons why people believe that the will is not causally determined. The last of these is religion. Here, Hume pivots to a different point. He says that moral responsibility is not just compatible with the causal determination of the will. Rather, the causal determination of the will is essential to moral responsibility.
This is where he makes his claim about character. He says that punishment, either human or divine, would be unjust if we did not discriminate between actions that are consistent with someone’s character and those that are due to more fleeting or erratic motivations. The former can be attributed to the person while the latter, usually, cannot. We will want to talk about his reasoning here (2.3.2 par. 6).