In his ‘Treatise’, Hume targets rationalism and is most noted for saying that ‘reason is the slave of the passions’ and challenging the thought held that morality is discovered by the use of reason. Hume is an empiricist, and his ideas about the passions are said to have influenced Kant in his rationalist argument for the Categorical Imperative.

Rationalism says that reason and sentiment (also known as the passions) are in a constant fight against one another to control our actions and that, in the end, it is reason that triumphs over the transient nature of the passions (our emotions and feelings). Thus it is reason that is the source of our justification for actions and in our determining which actions are moral. In direct contrast, Empiricism says that experience, especially that gained by the senses, is the main method used in the formation of ideas. As such, says Hume, morals are derived from sentiments – feelings or approval or disapproval that are felt towards some action or person. Although Hume does say that reason is necessary to discover the facts about different situations and to organise general social rules in the greater scheme of things, for an action to have moral worth, it must be based on a desire or ‘passion’ which motives us to act.

“Reason is, and ought only to be, the slave of the passions and can never pretend to any other office than to serve and obey them” (T2.3.3, p753)

Hume says that reason has no part at all in determining our ends

Some other philosophers have held that the necessity for us to act morally is, neither by reason nor the senses, but by divine revelation (God’s will). Others hold that it is by reflection on our conscience and the structure of human nature that we are required to act morally. Hume agrees that it is down to our nature as human beings (the ability to feel both pleasure and pain, the interdependence on other people such as our family, friends and co-workers) that makes us have moral obligations. Furthermore, Hume distinguishes between morality being something that is forced upon us by society (politicians or governments) in order to keep us in line and the natural inclination to act in a moral manner. He says that it must be the latter, because otherwise where would such concepts of virtues and acting in a correct manner come from? If we do not have the natural inclination to act humanely as part of a community to begin with, we would not be able to conceive of further social rules to govern societies.

On the Passions, the Will and Morality

So Hume sets out to prove that (1) “reason alone can never be a motive to any action of the will;” and (2) “that it can never oppose passion in the direction of the will” (T2.3.3, p752). He goes on to asset that reason is motivationally inert; while it may help us with a great many things, from mathematics to logic, probability and other abstract relations of ideas and the causal relations of real objects in the world, it does not cause nay action. Because reason cannot produce a motive, neither can it oppose a motive. This is because, in order to oppose a motive, there must be another motive which acts against it. But we have said that reason does not produce any motive, so be the same token it cannot produce an opposing motive.

There are two instances where our passions may be called unreasonable: “First, when a passion, such as hope or fear, grief or joy, despair or security, is founded on the supposition of the existence of objects, which really do not exist. Secondly, when in exerting any passion in action, we choose means insufficient for the designed end, and deceive ourselves in our judgement of causes and effects” (T2.3.3, p753-4). He goes on to make another famous claim:

“It is not contrary to reason to prefer the destruction of the whole world to the scratching of my finger” (T2.3.3, p754).

Here Hume is saying that reason does have a subordinate role in our actions; it tells us how we can satisfy our passions. If our passions are based on false beliefs (for example, believing in objects that aren’t really there) or are based on mistakes in ‘means-end reasoning’ (coming to false conclusions about the effects of our actions), then we will end up will passions (desires) to do things which are contrary to reason. In other words, we make errors in our judgements about situations (we are only human after all), and this gives rise to feelings that attempt to avoid those causes that will make us feel pain. Similarly, for pleasure, we judge that an action will give rise to pleasure and our emotion naturally extends itself to attain the pleasure. But note that it is not the passion itself that is unreasonable, but our judgement or ‘causal reasoning’ about the situation.

For example, I see a a glass of clear liquid and conclude that it is water and want to quench my thirst. But you convince me that it is actually ethanol and would not be advisable to drink it. Hence, my passion (the desire to drink the liquid) is based on a false supposition. As soon as I realise this falsehood, my reason directs me to a different passion, the desire not to drink it. So it is not reason that motivates me not to drink, it merely convinces me of my mistake. The motivation not to drink come from a different desire that urges me not to drink.

But what stops me from acting immorally or satisfying my many selfish desires if it is not reason that does so? Hume says it is not reason, but ‘calm passions’ or ‘calm tendencies’ that do so. ‘Violent emotions‘ are those we feel evidently, like the rush of anger when someone insults us or pang of jealousy when we see someone we like in the arms of other person. These are our obvious passions, but there are others: ‘Calm desires‘ might be things like benevolence and resentment, kindness to children (etc). Hume says that because these passions are ‘calm’ and do not cause much disturbance within us, so we often mistake them for reason, but they are nevertheless there. Even though they do not produce much emotion in our minds, they are there in our nature, such as the general willing to live harmoniously with others and the propensity for pleasure over pain.

He goes on to talk of the motivation of morals: “Morals excite passions, and produce or prevent actions. Reason of itself is utterly impotent in this particular. The rules of morality, therefore, are not conclusions of reason” (T3.1.1, p756). Reason cannot motivate us to act, as we have seen, but moral judgements do cause us to act, so reason cannot be the source of moral good and evil. To elaborate on this, consider that we think of moral judgements as being worthy of praise and blame, but factual statements derived from reason do not incite such emotions. In other words, moral mistakes do not seem to be in the same domain as factual errors because we do not ascribe emotive responses like praise and blame to factual errors. Therefore moral judgements are not truth apt – they are not capable of being true or false because they are not facts or realities.

Morality is not based in facts; we don’t find evidence in the world for existence of good and bad facts or laws. They are all down to the passions, volitions and motives of individual agents. Virtue and vice are found by considering the thoughts and feelings we have as people and in the thoughts and feelings of other individuals. They may not be properties in objects, but dependent on the views of different people and our perspective as human beings (in the same way colours might be – see Moral Realism). In a famous passage Hume says:

“Take any action allowed to be vicious; wilful murder, for instance. Examine it in all lights, and see if you can find that matter of fact, or real existence, which you call vice. In whichever way you take it, you only find certain passions, motives, volitions, and thoughts. There is no other matter of fact in the case. The vice certainly escapes you, as long as you consider the object. You can never find it, till you turn your reflection into your own breast, and find a sentiment of disapprobation, which arises in you, towards this action” (T3.1.1, p761)

Further consider that, if morality were derived from reason, then any statements that we could suppose from reason would be subject to our moral judgements. For example, as mentioned in my lecture: “Young oak trees could be convicted of patricide, and animals could be convicted of ‘moral turpitude’ for mauling each other” (Dr. Lang). But clearly convicting animals or trees of immorality is insane, so it seems to point to the need for motives, or passions, in our actions for them to hold moral worth.

But we might reply to this by saying that reasons are limited only to beings that are capable of making judgements about situations. Animals and trees clearly are not.

Moral Sense

Hume later goes on to talk more about our moral sense and discrimination. He says:

“Morality…is more properly felt than judged of; though this feeling or sentiment is commonly so soft and gentle that we are apt to confound with an idea, according to our common custom of taking all things for the same which have any near semblance to each other” (T3.1.2, p762).

He then asks a general nature about the nature of the passions and says that “the impression arising from virtue [is being] agreeable, and that proceeding form vice [is being] uneasy” (T3.1.2, p762). Very basically, it is because of the very feeling we have when we take action in a particular situation that we call it virtue (a pleasurable feeling) or vice (an uneasy feeling).

But this view seems troublesome. Is acting on our feelings really a reliable way of viewing situations? We may see a man wearing black glasses and wearing a long overcoat hanging around a bank and feel threatened thinking he might be ready to rob the bank, but actually it turns out he is the security guard. Are feelings free from partiality and are they fine-grained enough for the wide variety of moral judgements there are? We may feel one type of ‘pleasure’ from eating good food to saving a drowning child?

Hume says that “it is only when a character is considered in general, without reference to our particular interest, that it causes such a feeling or sentiment as denominates it morally good or evil” (T3.1.2, p762). So to solve the problems above, Hume is saying that we must consider the person or situation in general, not just focussing on the feelings that we have in one particular situation.

The praise and blame that we attribute to an action are decided by the moral quality of the action. In other words, the motives behind the action: “all virtuous actions derive their merit only from virtuous motives, and are considered merely as signs of those motives”. But such motives must be natural motives, or principles. They must have something general, or independent of the situation at hand that makes them morally worthwhile. Hume says that:

“When any virtuous motive or principle is common in human nature, a person who feels his heart devoid of that motive, may hate himself upon that account, and may perform the action without the motive, from a certain sense of duty, in order to acquire, by practice, that virtuous principle, or at least to disguise to himself, as much as possible, his want of it” (T3.2.1, p 765).

Here we see Hume mentioning the possibility of acting form duty, but such actions would only be second best to acting from one’s natural motives.

However, what about in the case of lending someone money. What reason or motive do we have to repay the money? We cannot just say because it is the honest action to take because there seems to be no natural motive of honesty in the same way that there is for other motives. We don’t feel the need to repay the money out of self interest, nor in the interests of the public (as the deal may be done in secret). A dutiful motive to be honest seems to be irreducible, and Hume says that “the sense of justice and injustice is not derived form nature, but arises artificially, though necessarily, from education and human conventions” (T3.2.1, p767).

This is the distinction between ‘Natural virtues’ – traits useful to people whether or not they are living in a society, and ‘Artificial virtues’ – traits that emerge as useful in large social groups and where social cooperation is needed among people. Natural virtues are, by nature, better become they give us a sense of satisfaction, but artificial virtues benefit people with their widespread implications in a community. Hume says that the rules of justice arise from the selfishness and limited generosity of human beings and the tendency for situations to change and scarcity of external resources. As such, the motive of self-interest is switched for a motive of duty in these larger public situations due to the public good needed to be served.

Lastly, a brief note about what Hume says on Freedom. Hume is traditionally seen as a compatibilist about freedom. He argues that all human actions are products of causal necessity, but at the same time, we are all free. Just as the movements between material bodies are causally connected (a billiard ball striking another), so too are the connections between human motives and circumstances and behaviour causally linked.

Consider an individual who has killed another person. If the person did so on purpose, then according to Hume, they have an some enduring passion or character trait that is bad and that is the cause of their committing murder. But if they did so by accident, then the individual will not incur blame. As individuals, we have choice as to whether or not we act in a given situation, but are still causally affected by our passions and the determinations in our will. So ultimately, we have freedom to act or not to act, but are (in both a moral and general sense) still bound by causal laws – the two are compatible, hence ‘compatibilism’.

Problems for Hume

Hume seems to suggest that reason is theoretical reason – it can only give rise to our beliefs about the world, but not reasons for action. Passions are not like beliefs because they are not based on facts (are not truth-apt) – they motivate us to act. But why do we have to assume that reason is restricted to the purely theoretical domain? Why not say that there is a practical form of reason?

Just because Hume may have been right to say that passion always features in our actions, it does not follow that passion is always the source of one’s doing something. Can’t we distinguish between unmotivated desires and motivated desires? We have unmotivated desires like those of appetite and stretching, and also motivated desires which are the results of considerations about different things, for example, thinking about going on strike opposing a war. We are not motivated to go on strike in the same way we are to stretch out our arms when we wake up in the morning.

Also, what about cases of depression and people who do not have a strong will, or worse are apathetic and cannot actually feel emotion. Are we to label them as immoral because they do not have the correct passionate responses to circumstances?

Instrumentalism

Some people have labelled Hume as an instrumentalist, but it is debatable as to whether or not he was. But as a theory, instrumentalism looks more plausible than following Hume and denying reason any role in our moral judgements. For an instrumentalist, Hume’s claim that ‘reason is the slave of the passions’ allows that, not only does reason discover the means to our ends (the circumstances and causal links in different situations), it also requires us to take these means. An instrumentalist says that:

(1) there are no ends that we ought to have and no ends dictated by reason
(2) but for the ends that we do have, we ought to take effective measures to fulfil them

In other words, we ought to take the means to my ends. But, for Hume, both ‘ends’ (normatively unconstrained passions) and ‘means to ends’ (normatively constrained passions) are put into the same category and as such fall outside the scope of reason.

Furthermore, Korsgaard raises the possibility of irrationality in one’s actions. Hume does not account for this when he says that:

“The moment we perceive the falsehood of any supposition, or the insufficiency of any means our passions yield to reason without any opposition…whenever you convince me of my mistake, my longing ceases” (T2.3.3, p754)

Hume doesn’t speak of changing our behaviour once reason has shown us the flaw in our judgement because it’s ‘irrational’, he merely says our emotion ‘naturally extends itself’ to do some action. But if reason is supposed to be the slave of the passions, why does a discovery of a flaw in our judgement by reason cause our passions to change? What is the link between our passions ‘naturally’ changing and our reason discovering some logical flaw?

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Sources: Lecture handouts written by my lecturer Dr. Gerald Lang, The Stanford Encyclopedia of Philosophy and ‘Classics of Moral and Political Philosophy’ (2005) by Michael Morgan