In the Treatise of Human Nature, David Hume famously argues that ‘reason is the slave of the passions’ and therefore cannot be the source of our moral decision making process. This post will consider Hume’s notion of ‘reason’ in more detail and whether his arguments are successful in establishing that reason is subservient to the passions as the source for our moral actions. If this is true, can reason play any role in moral decision making?
This discussion takes place over two books in the Treatise. Book 2 discussions the general relationship between reason and passion while Book 3 looks at the more specific case of morality. This post will argue that Hume’s notions can be criticised on a number of levels, in particular that it doesn’t agree with our everyday sense that reason does in fact play a vital role in deciding whether to act in a certain way. Whenever we are forced to make tough moral decisions, it would seem that reason ultimately prevails over self-interest.
Firstly, I want to consider Hume’s arguments for the role of reason in the decision making process. Although the Book 2 discussion is not specific to morality, in Book 3 Hume confirms that the same reasoning applies for moral decision making. Hume states in Book 2 the following two propositions: (1) that reason alone can never be the source of our actions, and (2) reason can never override passions once the passions have decided on a particular course of action. Each of these propositions will be considered separately.
In terms of the first proposition, Hume gives ‘reason’ a very restricted definition of two aspects only: (1) demonstrative knowledge, and (2) probable reasoning based on cause-and-effect. In the case of demonstrative knowledge, all reason can tell us is whether statements are true or false. It cannot motivate us into action. Similarly in the case of probable reasoning, all reason can tell us is that a relationship of cause-and-effect exists. Again, this is insufficient to motivate us into action, so reason cannot be the primary source of our actions.
We can question Hume here on whether his definition of reason is too restrictive. Is reason really just limited to those two areas alone? As discussed in other posts, what about some mental process like creativity? Doesn’t this rely on reason, at least partially? Nevertheless, Hume is convinced that he has proven that reason alone can never be the primary source of our passions. As I’ll shortly discuss, this may not rule out reason entirely from the decision making process, but it does reduce its importance.
In terms of the second proposition – that reason can never override the passions – Hume contends here that both reason and passions are different types of entities, speaking different types of languages. As stated above, reason is concerned with true/false statements, whereas the passions are an ‘original existence’ and cannot be reduced to statements of logic. Therefore, we cannot say that reason is in conflict with the passions since the two operate in different modes. Hume may be correct in thinking that reason and passion operate in different ways, but even so, is it correct to say that the passions are paramount and that reason can only ever be subservient to the passions? Our intuition indicates that reason can often conflict with passion. For instance, we may be tempted to have a night of heavy drinking. Reason tells us that we won’t feel well the following day if we do so, but nevertheless we go ahead with the drinking. Can we not say in this case that reason and the passions are in direct conflict?
Hume would respond to this by claiming that when a conflict does occur, it’s actually not reason and passion which are in conflict, but two passions on their own. Hume claims that a lot of the weaker passions have a similar effect to reason, so when the conflict does occur, we mistakenly think that the weaker passion is reason.
Using the same example as above, how could we agree with Hume and claim that two passions are actually in conflict with each other? We certainly have the stronger passion that we want to drink alcohol, but what is the passion that’s telling us not to drink? Is it possibly a form a pride? Do we suspect that our reputation could be adversely affected if we lose control of ourselves, so we ‘reason’ with ourselves that the night of heavy drinking isn’t a good idea? Hume could be saying that in cases where one of our passions is quite weak, reason steps in to try to support the weaker passion and override the stronger passion. However, Hume is unclear as to exactly what role reason plays when two passions are in conflict. Does reason act as a kind of ‘umpire’ trying to resolve the two conflicts, or does it play no role at all?
This leads to another question important question that comes up with Hume. Just what sort of role can reason play in the decision making process? Recall that when Hume was trying to show that reason is not the source of our decision making, he specified that ‘reason alone’ cannot do this. The ‘alone’ suggests that Hume is still willing to allow reason to play some part in moral decision making, possibly even a significant part. In addition, when he talks about the passions making a decision that turns out to be incorrect, he notes this happens because reason reached the wrong decision to being with. The passions cannot be said to be ‘wrong’ because they are not based on true / false statements. This appears to open the door for reason to continue having a strong influence in the decision making process, so perhaps Hume’s theory is not as limiting as it first appears. Hume may be offering more of a hybrid theory between reason and passions, which may more suit about natural intuitions.
In summary then, if we interpret Hume as saying that reason is completely subservient to the passions, then we can question Hume as to whether he has given reason an important enough role. Perhaps he has been too limited in his definition of reason, and perhaps he has been too dismissive of the rule of our rational mind (in an attempt to justify his theory that the passions are paramount). On the other hand, if we read some of his examples as allowing reason to continue playing an important role – even if the original decision is ‘sparked’ by the passions – then we can agree that Hume offers a plausible account of the role of reason in moral decision making. Reason on its own cannot motivate us to act. We do need the additional motivation of the passions to force us to act, even if the passion is simply a case of wanting to maintain a good reputation in front of others.