David Hume | Philosophy

David Hume (1711—1776)

David Hume was a Scottish philosopher, historian, economist, and essayist who was best known for his highly influential system of empiricism, philosophical skepticism and metaphysical naturalism. Beginning with A Treatise of Human Nature (1739–40), Hume strove to create a naturalistic science of man that examined the psychological basis of human nature. Hume followed John Locke in rejecting the existence of innate ideas, concluding that all human knowledge derives solely from experience. This places him with Francis Bacon, Thomas Hobbes, John Locke, and George Berkeley as an empiricist.

Hume argued that inductive reasoning and belief in causality cannot be justified rationally; instead, they result from custom and mental habit. We never actually perceive that one event causes another but only experience the "constant conjunction" of events. This problem of induction means that to draw any causal inferences from past experience, it is necessary to presuppose that the future will resemble the past; this metaphysical presupposition cannot itself be grounded in prior experience.

An opponent of philosophical rationalists, Hume held that passions rather than reason govern human behaviour, famously proclaiming that "Reason is, and ought only to be the slave of the passions." Hume was also a sentimentalist who held that ethics are based on emotion or sentiment rather than abstract moral principle. He maintained an early commitment to naturalistic explanations of moral phenomena and is usually accepted by historians of European philosophy to have first clearly expounded the is–ought problem, or the idea that a statement of fact alone can never give rise to a normative conclusion of what ought to be done.

Hume denied that humans have an actual conception of the self, positing that we experience only a bundle of sensations, and that the self is nothing more than this bundle of perceptions connected by an association of ideas. Hume's compatibilist theory of free will takes causal determinism as fully compatible with human freedom. His philosophy of religion, including his rejection of miracles, and of the argument from design for God's existence, were especially controversial for their time. Hume left a legacy that affected utilitarianism, logical positivism, the philosophy of science, early analytic philosophy, cognitive science, theology, and many other fields and thinkers. Immanuel Kant credited Hume as the inspiration that had awakened him from his "dogmatic slumbers."

The early modern period was the heyday of the investigation of the ideas of causation, moral good and evil, and many other philosophically contested ideas. Every modern philosopher accepted some version of the theory of ideas—the view that we immediately perceive certain mental entities called ideas, but don’t have direct access to physical objects. Hume holds an empiricist version of the theory, because he thinks that everything we believe is ultimately traceable to experience. He begins with an account of perceptions, because he believes that any intelligible philosophical question must be asked and answered in those terms. He uses perception to designate any mental content whatsoever, and divides perceptions into two categories, impressions and ideas.

Impressions include sensations as well as desires, passions, and emotions. Ideas are “the faint images of these in thinking and reasoning”. He thinks everyone will recognize his distinction, since everyone is aware of the difference between feeling and thinking. It is the difference between feeling the pain of your present sunburn and recalling last year’s sunburn.

Hume distinguishes two kinds of impressions: impressions of sensation, or original impressions, and impressions of reflection, or secondary impressions. Impressions of sensation include the feelings we get from our five senses as well as pains and pleasures, all of which arise in us “originally, from unknown causes”. He calls them original because trying to determine their ultimate causes would take us beyond anything we can experience. Any intelligible investigation must stop with them.

Impressions of reflection include desires, emotions, passions, and sentiments. They are essentially reactions or responses to ideas, which is why he calls them secondary. Your memories of last year’s sunburn are ideas, copies of the original impressions you had when the sunburn occurred. Recalling those ideas causes you to fear that you’ll get another sunburn this year, to hope that you won’t, and to want to take proper precautions to avoid overexposure to the sun.

Perceptions—both impressions and ideas—may be either simple or complex. Complex impressions are made up of a group of simple impressions. My impression of the violet I just picked is complex. Among the ways it affects my senses are its brilliant purple color and its sweet smell. I can separate and distinguish its color and smell from the rest of my impressions of the violet. Its color and smell are simple impressions, which can’t be broken down further because they have no component parts.

Hume initially distinguishes impressions and ideas in terms of their degree of force and vivacity. Impressions are more forceful and vivacious than ideas. My impression of this ripe tomato’s bright red color is as vivid as anything could be. Last year’s tomatoes were just as vivid when I was looking at them, but now my idea of them is much less vivid than my impressions of the tomato in front of me. Since last year’s tomatoes were the same color, the difference can’t be that they are different shades of red; the difference must lie in the sharpness, clarity, and brightness of my impressions—their force and vivacity. At various times, Hume tries other ways of characterizing the difference between impressions and ideas, but he was never completely satisfied with them. Still, what he says works well enough to give us a handle on the felt differences between impressions and ideas.

When Hume distinguishes impressions and ideas in terms of their relative force and vivacity, he is pointing out something that is generally true of them as a matter of fact. On occasion, in dreams or a high fever, ideas may approach the force and vivacity of impressions, but these are exceptions that prove the—empirical—rule. In general, impressions and ideas are so different that no one can deny the distinction.

Although nothing seems freer than the power of thought, which isn’t “restrained within the limits of nature and reality” (EHU 2.4/18), Hume insists that our imagination is in fact “confined within very narrow limits”. We can separate and combine our ideas in new and even bizarre ways, imagining creatures we’ve never seen or faraway galaxies, but all the materials of thinking are ultimately derived from our impressions. Since “all our ideas or more feeble perceptions are copies of our impressions or more lively ones”; we are restricted to “compounding, transporting, augmenting, or diminishing the materials afforded us by the senses and experience”.

Hume’s explanation of morality is an important part of his efforts to reform philosophy. He takes his primary task to be an investigation into the origin of the basic moral ideas, which he assumes are the ideas of moral goodness and badness. As with the idea of cause and necessary connection, he wants to explain moral ideas as economically as possible in terms of their “simplest and fewest causes”. Determining their causes will determine what their content is—what we mean by them. His secondary concern is to establish what character traits and motives are morally good and bad.

Hume follows his sentimentalist predecessor, Francis Hutcheson (1694–1746), in building his moral theory around the idea of a spectator who approves or disapproves of people’s character traits and motives. The sentiments of approval and disapproval are the source of our moral ideas of goodness and badness. To evaluate a character trait as morally good is to evaluate it as virtuous; to evaluate it as morally bad is to evaluate it as vicious.

As he did in the causation debate, Hume steps into an ongoing debate about ethics, often called the British Moralists debate, which began in the mid-seventeenth century and continued until the end of the eighteenth. He uses the same method here as he did in the causation debate: there is a critical phase in which he argues against his opponents, and a constructive phase in which he develops his version of sentimentalism. Hume has two sets of opponents: the self-love theorists and the moral rationalists. He became the most famous proponent of sentimentalism.

Thomas Hobbes’ (1588–1679) radical attempt to derive moral and political obligation from motives of self-interest initiated the British Moralists debate. Hobbes, as his contemporaries understood him, characterizes us as naturally self-centered and power-hungry, concerned above all with our own preservation. In the state of nature, a pre-moral and pre-legal condition, we seek to preserve ourselves by trying to dominate others. Since we are all sufficiently “equal” in power, this results in a state of “war of all against all” in which life is “nasty, brutish, and short” (Leviathan, Ch. 13). The way out is to make a compact with one another. We agree to hand over our power and freedom to a sovereign, who makes the laws necessary for us to live together peacefully and has the power to enforce them. While acting morally requires that we comply with the laws the sovereign establishes, the basis of morality is self-interest.

Bernard Mandeville’s (1670–1733) The Fable of the Bees served to reinforce this reading of Hobbes during the early 18th century. According to Mandeville, human beings are naturally selfish, headstrong, and unruly. Some clever politicians, recognizing that we would be better off living together in a civilized society, took up the task of domesticating us. Realizing that we are proud creatures, highly susceptible to flattery, they were able to dupe many of us to live up to the ideal of virtue—conquering our selfish passions and helping others—by dispensing praise and blame. Moral concepts are just tools clever politicians used to tame us.

Two kinds of moral theories developed in reaction first to Hobbes and then to Mandeville—rationalism and sentimentalism. The rationalists oppose Hobbes’ claim that there is no right or wrong in the state of nature, that rightness or wrongness is determined by the sovereign’s will, and that morality requires sanctions to motivate us. The sentimentalists object to Hobbes’ and Mandeville’s “selfish” conceptions of human nature and morality. By the mid–eighteenth century, rationalists and sentimentalists were arguing not only against Hobbes and Mandeville, but also with each other.

Hume opposes both selfish and rationalist accounts of morality, but he criticizes them in different works. In the Treatise, Hume assumes that Hobbes’ theory is no longer a viable option, so that there are only two possibilities to consider. Either moral concepts spring from reason, in which case rationalism is correct, or from sentiment, in which case sentimentalism is correct. If one falls, the other stands. In the second Enquiry, Hume continues to oppose moral rationalism, but his arguments against them appear in an appendix. More importantly, he drops the assumption he made in the Treatise and takes the selfish theories of Hobbes and Mandeville as his primary target. Once again, he thinks there are only two possibilities. Either our approval is based in self-interest or it has a disinterested basis. The refutation of one is proof of the other.

Hume thinks that “systems and hypotheses” have also “perverted our natural understanding” of morality. The views of the moral rationalists—Samuel Clarke (1675–1729), Locke and William Wollaston (1660–1724)—are prominent among them. One distinctive, but unhealthy, aspect of modern moral philosophy, Hume believes, is that it allies itself with religion and thus sees itself as serving the interests of “popular superstition”. Clarke’s theory and those of the other rationalists epitomize this tendency.

Clarke, Hume’s central rationalist opponent, appeals to reason to explain almost every aspect of morality. He believes that there are demonstrable moral relations of fitness and unfitness that we discover a priori by means of reason alone. Gratitude, for example, is a fitting or suitable response to kindness, while ingratitude is an unfitting or unsuitable response. He believes that the rational intuition that an action is fitting has the power both to obligate us and to move us. To act morally is to act rationally.

Hume’s most famous and most important objection to moral rationalism is two-pronged. In Treatise 2.3.3, “Of the influencing motives of the will”, he rejects the rationalist ideal of the good person as someone whose passions and actions are governed by reason. In T 3.1.1, he uses these arguments to show that moral ideas do not spring from reason alone.

In the first prong of his objection, Hume begins by remarking that nothing is more common than for philosophers, as well as ordinary people, to talk about the “combat” between reason and passion. They say we ought to be governed by reason rather than passion, and if our passions are not in line with reason’s commands, we ought to restrain them or bring them into conformity with reason. Hume counters that “reason alone can never be a motive to any action of the will” and that by itself it can never oppose a passion in the direction of the will.

His first argument rests on his empiricist conception of reason. As we saw in his account of causation, demonstrative reasoning consists in comparing ideas to find relations among them, while probable reasoning concerns matters of fact. He considers mathematical reasoning from the relation of ideas category and causal reasoning from the category of matters of fact. He asks us to look at instances of actions where these two types of reasoning are relevant and says that when we do, we will see that reason alone couldn’t have moved us.

No one thinks that mathematical reasoning by itself is capable of moving us. Suppose you want to stay out of debt. This may move you to calculate how much money comes in and how much goes out, but mathematical reasoning by itself does not move us to do anything. Mathematical reasoning, when it bears on action, is always used in connection with achieving some purpose and thus in connection with causal reasoning.

Hume, however, argues that when causal reasoning figures in the production of action, it always presupposes an existing desire or want. On his view, reasoning is a process that moves you from one idea to another. If reasoning is to have motivational force, one of the ideas must be tied to some desire or affection. As he says,

It can never in the least concern us to know, that such objects are causes, and such others effects, if both the causes and effects are indifferent to us. Where the objects themselves do not affect us, their connexion can never give them any influence; and ‘tis plain, that as reason is nothing but the discovery of this connexion, it cannot be by its means that the objects are able to affect us.

Noticing a causal connection between exercise and losing weight will not move you to exercise, unless you want to lose weight.

It immediately follows that reason alone cannot oppose a passion in the direction of the will. To oppose a passion, reason must be able to give rise to a motive by itself, since only a motive can oppose another motive, but he has just shown that reason by itself is unable to do this.

Having exposed reason’s pretensions to rule, Hume inverts the rationalist’s ideal of the good person, and concludes that “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”.

The second prong of Hume’s objection, the argument from motivation, is directed primarily against Clarke and concerns the source of our moral concepts: either they spring from reason or from sentiment. Couching this debate in terms of his own version of the theory of ideas, he reminds us that to engage in any sort of mental activity is to have a perception before the mind, so “to approve of one character, to condemn another, are only so many different perceptions”. Since there are only two types of perception—ideas and impressions—the question between rationalism and sentimentalism is whether this is by means of our ideas or impressions we distinguish between vice and virtue, and pronounce an action blameable or praise-worthy?

The argument from motivation has only two premises. The first is that moral ideas have pervasive practical effects. Experience shows that we are often motivated to perform an action because we think it is obligatory or to refrain because we think it is unjust. We try to cultivate the virtues in ourselves and are proud when we succeed and ashamed when we fail. If morality did not have these effects on our passions and actions, moral rules and precepts would be pointless, as would our efforts to be virtuous. Thus “morals excite passions, and produce or prevent actions”.

The second premise is that by itself reason is incapable of exciting passions or producing and preventing actions, which Hume supports with the arguments we just looked at about the influencing motives of the will. The argument from motivation, then, is that if moral concepts are capable of exciting passions and producing or preventing actions, but reason alone is incapable of doing these things, then moral concepts can’t spring from reason alone.

Reason for Hume is essentially passive and inert: it is incapable by itself of giving rise to new motives or new ideas. Although he thinks the argument from motivation is decisive, he offers a battery of additional arguments, which are intended to show that moral concepts do not arise from reason alone.

Hume takes the defeat of rationalism to entail that moral concepts spring from sentiment. Of course, he was not the first to claim that moral ideas arise from sentiment. Hutcheson claimed that we possess, in addition to our external senses, a special moral sense that disposes us to respond to benevolence with the distinctive feelings of approbation. Hume, however, rejects the idea that the moral sentiments arise from a sense that is an “original quality” and part of our “primary constitution”.

He first argues that there are many different types of virtue, not all of which are types of benevolence—respecting people’s property rights, keeping promises, courageousness, and industriousness—as Hutcheson maintained. If we agree with Hume, but keep Hutcheson’s idea of a moral sense, we would have to believe that we have many different “original” senses, which dispose us to approve of the variety of different virtues separately. But he complains that this is not only highly implausible, but also contrary to the

usual maxims, by which nature is conducted, where a few principles produce all the variety we observe in the universe.

Instead of multiplying senses, we should look for a few general principles to explain our approval of the different virtues.

The real problem, however, is that Hutcheson just claims—hypothesizes—that we possess a unique, original moral sense. If asked why we have a moral sense, his reply is that God implanted it in us. Although in his critical phase Hume freely borrows many of Hutcheson’s arguments to criticize moral rationalism, his rejection of a God-given moral sense puts him on a radically different path from Hutcheson in his constructive phase. One way of understanding Hume’s project is to see it as an attempt to naturalize Hutcheson’s moral sense theory. He aims to provide a wholly naturalistic and economical explanation of how we come to experience the moral sentiments that also explains why we approve of the different virtues. In the course of explaining the moral sentiments, Hutcheson’s idea of an original moral sense disappears from Hume’s account of morality.

Quotes by Hume:

Be a Philosopher; but, amidst all your Philosophy, be still a Man.
To hate, to love, to feel, to see; all this is nothing but to perceive.
Generally speaking, the errors in religion are dangerous; those in philosophy only ridiculous.
But the life of a man is of no greater importance to the universe than that of an oyster.
A wise man proportions his belief to the evidence.
There is no such thing as freedom of choice unless there is freedom to refuse.
It is an absurdity to believe that the Deity has human passions, and one of the lowest of human passions, a restless appetite for applause.
Revolutions of government cannot be effected by the mere force of argument and reasoning.