Reason Alone Cannot Move Action

The wider causal reason comes in for attack when Hume turns to look at human morality.¹⁵ Hume asserts a) that causal (and a fortiori narrow-sense) reason cannot move people to act; b) that moral evaluations clearly can move people to act;¹⁶ and therefore c) that the making of moral distinctions is not only a rational process as is often claimed.

From Plato onwards traditional moral doctrine has sounded variations on a theme, one in which humans ought to control their emotions by reason; in which true virtue lies in conformity to reason; in which external, objective moral relations of fitness can be discerned by reason; in which belief was the result of rational argument; and in which human worth itself depends on the extent to which one can be guided by reason. Reason, in short, had traditionally been given a pre­eminent place in moral life when Hume came to write; indeed this according of pre-eminence perhaps remains the orthodoxy. Hume’s own formulation of the traditional view, in the first paragraph of the Treatise's famous Book II iii 3, is as good as any. However, Hume argues that this traditional conception is simply wrong because reason, broad or narrow, is completely inert. There is no struggle between passion and reason, no victory by the latter, because reason can never even conflict with passion.

In order to show the fallacy of all this philosophy, I shall endeavour to prove first, that reason alone can never be a motive to any action of the will; and secondly, that it can never oppose passion in the direction of the will.¹⁷

Hume then makes explicit the dichotomy detailed above that the understanding, or reasoning, has two branches: the branch which judges from demonstration the abstract relations of ideas (narrow­sense reason) and the branch which judges from probability those relations of objects of which experience only gives information (broad-sense or causal reason). The former is evidently, thinks Hume, never a cause of action. Its sphere is the world of ideas. Only in helping to work out effects and causes (say through mathematics in solving mechanical operations) can it influence action, and this is in the realm of, and leads Hume to examine, causal reasoning.

Hume goes on to argue that broad reason, the process of determining likely ends and best means which leads to empirical knowledge, cannot give rise to volition. It can influence action — by revealing probable consequences — but can never provide the original impulse. Pleasure, pain or any underived want or desire can produce or prevent action. Reason cannot. Reason could oppose volition only by setting up a contrary one — which it cannot do. It will not matter to me that I know where to find the refrigerator or how to plead successfully for my sister to wait on me unless I happen to want a beer. Every action, however much guided and influenced by deep pondering and measured debate {e.g. the bombing of Hiroshima or the selecting of Nobel prize winners), still requires some pre-existing desire as motivating force. Thus, “[w]e speak not strictly and philosophically when we talk of the combat of passion and of reason.”¹⁸ And this inability of reason to operate at all without some propensity or desire on which to fasten is what Hume means when he says, “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.”¹⁹

That there must be an aversion or propensity present in all cases of action is, to my mind, correct.

To the extent that Hume strictly links the motivating cause of action — let us call that a propensity, preference, sentiment, or desire — to the existence of a felt passion he may get himself into trouble, as Stroud argues. The theory of ideas demands particular mental units, distinct perceptions, like passions. But nowhere does Hume show that preferences, propensities or desires are the same as, nor need they be envisaged as, passions. My preferring the destruction of the whole world need not be explained in terms of my holding a passion or conscious feeling.²¹ So Hume’s further conclusion that people are moved to act by a passion does not follow from the correct and true conclusion that people only act if they are not indifferent; if they desire or prefer some X over Y. Conversely, however, whether or not propensities, sentiments, desires or preferences be passions (conscious feelings) does not bear on the more important issue of whether reason alone can produce propensities, sentiments, desires or preferences.

Stroud also is helpful in noting that reason is more than a set of propositions or beliefs with truth-value. Reasoning is also a mental process, a discovery process, involving a certain attitude towards the propositions believed.

So the important issue, I suggest, is whether it is ever possible to move from reasoning to believing to wanting to acting or whether there must always be some underlying underived want. My position is that reason (broad or narrow) produces a want or propensity only where there was already a want or propensity and that any regressive analysis of actions must always come to rest at some underived want.²² Such a want need not be limited to pain or pleasure. Hume himself divided off a large number of ‘passions’ or wants, including vengeance, benevolence, lust, love of life and kindness to children, as not arising from pleasure or pain but merely as core level, unanalysable proclivities or ‘passions’. Such a non-Benthamic premiss is still consistent with the view that every action a human can perform involves a want and reasoning can only produce that want where some other want already existed. (For example, wanting a promotion I can discover by causal reasoning that publishing many articles, regardless of quality, is the best way to achieve it and thus come to want to publish many articles.) As Stroud notes, “Something must be wanted on its own account, and not just as a means to, or as a way of, getting something else one wants.”²

This fundamental point of Hume’s, on the impotence of either type of reason as the sole motive of action, must surely be accepted unless and until those who disagree can give examples of how broad or narrow reason can ever, all alone with no existing want of any kind, move someone to act.

A paramount challenge then, for anyone for whom reason and rationality are thought to do more, is to explain how reason, alone, can create underived wants. If reason (of either Humean type) cannot by itself produce a motivating propensity, then even the claims of morality — the ‘oughts’ and ‘shoulds’ — would seem to be linked to human sentiments. And if all action, even moral action, requires at core some underived sentiment, propensity, desire or passion then what we humans can be motivated to do (even by moral claims) depends on how we humans happen to feel. This, though, is the language and outlook of contingency, of nothing being more solid or ‘right’ than observed majority sentiments. Hence a fundamental challenge for the anti-Humean is to show how reason alone can move people to act.

In the rest of this chapter I will recap the Humean attack on the pretensions of reason and then review aspects of this concept of reason for the first time before considering one particular attempt to show whether reason alone can create underived wants and motivate action. The purpose of this discussion of the scope of reason, it will be recalled, is to arrive at a defensible view of the powers of reason which will serve as a preliminary foundation to a view of human beings and thus to a moral theory and eventually to a theory of law.

In a nutshell this is Hume’s position on reason.

It is this process of generalising from cause to effect and back which is causal, broad-sense reason. Humans are distinctively rational, not because some metaphysical reason rules over desire and sentiment, but because humans far better than all others are able to calculate future events based on past events. No other animal is nearly as proficient as we are at this, but it is merely a matter of degree and not of kind. Nor can reason move us to act. Hume argues that what is required is a passion or feeling. I agree that some sort of want or propensity is needed, even if the spur need not be envisaged in terms of a mental item. A Humean passion may not be the same as a propensity, desire, sentiment, or preference, but then neither is broad or narrow reason the same. Even the state of ‘believing’ requires some ‘wanting’ to result in ‘acting’. Isolated on its own, reason may not be merely representational but it is all the same impotent. In this form, I accept, and will defend, Hume’s major premiss that reason cannot alone dispose us to act.

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