In Book 3, Hume returns to the subject of reason and passions, but in the specific context of making moral decisions. The following propositions are considered:
- The source of all our moral actions is passion (a kind of moral sentiment)
- Reason plays a role in moral decision making, but its role is always subservient to that of moral sentiment
Firstly, Hume re-iterates his definitions of ideas and impressions. An impression includes sensory perceptions, as well as the passions and emotions. Ideas are the more permanent form of the impression, albeit weaker in power. The combination of ideas and impressions creates the category of ‘perceptions’.
Hume believes this gives rise to a natural question in terms of morality. When we distinguish between vice and virtue – judge something in moral terms – is this judgement based on ideas or impressions? According to the traditional view of philosophers, reason (the combination of ideas) is the source of our morality.
However Hume again rejects the role of reason. He briefly raises a number of supporting arguments, but none of these arguments are convincing. Firstly, if the passions had no part to play in the making of moral judgements, then why do we go to so much trouble to define and analyse moral rules? This suggests to Hume that our passions need as much advice as we can possibly provide them. However, you could argue that the same argument applies to reason. If reason governs our actions, then it too could benefit from a constant supply of rules and regulations.
Furthermore, Hume notes that morality generally falls under the realm of ‘practical philosophy’. This suggests that our moral actions go beyond the calm and detached judgements of reason and have an important role to play in the everyday world we live in. Hume believes this is also confirmed by what we observe in other people. We will see that people, for instance, are governed and deterred from action by feelings of injustice.
As part of this argument, Hume is asserting that the word ‘practical’ refers to a world of action, one in which reason plays a secondary role. However, it is far from certain if ‘practical’ really has such a meaning. If a surgeon is carrying out a ‘practical’ procedure, he is still heavily influenced by his experience and reason. Just because it appears from an objective viewpoint that an action is practical, this does nothing to rule out the influence of subjective rationality. So just because morality is classed as ‘practical philosophy’, this shouldn’t make us think that it’s a subject devoid of intellectual rigour.
Nevertheless, Hume in convinced that reason cannot be the source of our morals. ‘An active principle can never be founded on an inactive’. Reason is only concerned with truth based on agreement with a proposition. These concepts are irrelevant when talking about the passions. As already covered in Book 2 of the Treatise, it is incorrect to talk about the passions being ‘contrary or conformable’ to reason. Our moral decisions are instead based on a moral ‘sentiment’, akin to that of the senses, such as the way in which we understand intuitively whether something is hot or cold. When we approve of another person’s action, we feel pleasure; when we disapprove we feel pain. We then interpret this feeling of pleasure or pain as either virtue or vice.
Having confirmed the paramount status of passion, Hume believes he has completed his task. He has managed to prove the following: (1) he has proven that actions do not obtain their moral flavour from reason (the direct argument), and (2) he has proven that reason can never contradict the passions when making moral decisions (the indirect argument).
However, one major question we could ask of Hume concerns the original challenge that he set out to resolve, that of the relationship between passion and reason. Hume wanted to discover whether our actions are driven by reason or passions. He seems determined to find the answer in one or the other. In that respect then, he is not so different from the other philosophers he criticises, those who insist that reason alone is what drives action.
But what makes Hume or anyone else think that there is a single, definitive answer to the question? Could you not reasonably argue that actions consist of both components: a component of reason and a component of passion? Why must we assume that the answer lies in one realm alone? Furthermore, modern science supports the view that human minds are tightly integrated machines, which suggests it is becoming futile to even draw distinctions between reason and passions. Because the human mind ultimately comes down to the same biological processes, is it worth trying to pinpoint the source of action to one ‘part’ alone, as this will only be an artificial distinction at best?
Hume’s value however lies in refuting the commonly-accepted wisdom of humans as creatures of rationality. Even if we reject Hume’s more extreme position of the passions being the sole motivating force behind an action, we can still accept that Hume has made a significant contribution to the ‘science’ of human nature. Reason is perhaps not as influential as we might think, and it is folly to judge human beings as paradigms of rationality. As unpalatable as it might appear, we cannot avoid the strength of our passions and desires.