David Hume (April 26, 1711 – August 25, 1776) 
was a Scottish philosopher and historian and, with Adam Smith 
and Thomas Reid among others, one of the most important figures 
in the Scottish Enlightenment. Many regard Hume as the third and 
most radical of the so-called British Empiricists, after the 
English John Locke and the Anglo-Irish George Berkeley; this 
bracketing of Hume, Locke, and Berkeley, though traditional, 
ignores the major influence on Hume of various French and 
German writers such as Kant and Voltaire, as well as various 
other figures on the Anglophone intellectual landscape such 
as Isaac Newton, Samuel Clarke, Francis Hutcheson, and Joseph 
Butler.

Historians most famously see Humean philosophy as a thoroughgoing 
form of Scepticism, but many commentators have argued that the 
element of Naturalism has no less importance. Hume scholarship 
has tended to oscillate over time between those who emphasize 
the sceptical side of Hume (such as Reid, Greene, and the 
logical positivists), and those who emphasize the naturalist 
side (such as Norman Kemp Smith, Stroud, and Galen Strawson).

Career

Hume was born in Edinburgh and attended Edinburgh University. 
At first he considered a career in law, but came to have, in 
his words, "an insurmountable aversion to everything but the 
pursuits of philosophy and general learning".

He did some self-study in France, where he also completed A 
Treatise of Human Nature at the age of twenty-six. Although 
many scholars today consider the Treatise to be Hume's most 
important work and one of the most important books in the 
history of philosophy, the public in England did not at first 
agree. Hume himself described the (lack of) public reaction 
to the publication of the Treatise in 1739–40 by writing that 
the book "fell dead-born from the press".

After a few years of service to various political and military 
figures, Hume returned to his studies. After deciding that the 
Treatise had problems of style rather than of content, he 
reworked some of the material for more popular consumption in 
An Enquiry Concerning Human Understanding. It did not prove 
extremely successful either, but more so than the Treatise.

Hume failed to gain chairs of philosophy in Edinburgh and in 
Glasgow, probably due to charges of atheism, and to the 
opposition of one of his chief critics, Thomas Reid.

However, between philosophical pursuits, Hume did achieve literary 
fame as an essayist and historian. Attention to his works grew 
after no less a philosopher than Immanuel Kant credited Hume 
with awakening him from "dogmatic slumber" (circa 1770).

Legacy

Though Hume wrote in the 18th century, his work seems still 
uncommonly relevant in the philosophical disputes of today 
compared to that of his contemporaries. A summary of some of 
Hume's most influential work in philosophy might include the 
following:


The Problem of Causation

When one event causes another, most people think that we are 
aware of a connection between the two that makes the second 
event follow from the first. Hume challenged this belief, 
noting that whereas we do perceive the two events, we don't 
perceive any necessary connection between the two. And how 
else but through perception could we gain knowledge of this 
mysterious connection? Hume denied that we could have any 
idea of causation other than the following: when we see that 
two events always occur together, we tend to form an 
expectation that when the first occurs, the second will 
soon follow. This constant conjunction and the expectation 
thereof is all that we can know of causation, and all that 
our idea of causation can amount to. Such a lean conception 
robs causation of all its force, and some later Humeans like 
Bertrand Russell have dismissed the notion of causation 
altogether as something akin to superstition. But this 
violates common sense, thereby creating the problem of 
causation – what justifies our belief in a causal connection 
and what kind of connection could we have knowledge of? – a 
problem which has no accepted solution. Hume seems to have 
held the view that we (as well as other animals) have an 
instinct-like belief in causality based on the development 
of habits in our nervous system, a belief that we cannot 
eliminate but which we cannot prove true by any kind of 
argument, deductive or inductive, just as is the case with 
regard to our belief in the reality of the external world.

For relevant contemporary work, see Wesley Salmon's Hume 
and the Problem of Causation and Causality and Explanation.


The Problem of Induction

We all think that the past acts as a reliable guide to 
the future. For example, physicists' laws of planetary 
orbits work for describing past planetary behavior, so we 
presume that they'll work for describing future planetary 
behavior as well. But how can we justify this presumption – 
the principle of induction? Hume suggested two possible 
justifications and rejected them both:

   1. The first justification states that, as a matter of 
   logical necessity, the future must resemble the past. 
   But, Hume pointed out, we can conceive of a chaotic, 
   erratic world where the future has nothing to do with 
   the past – or, more tamely, a world just like ours right
   up until the present, at which point things change 
   completely. So nothing makes the principle of induction 
   logically necessary.
   2. The second justification, more modestly, appeals 
   only to the past reliability of induction – it's always 
   worked before, so it will probably continue to work. 
   But, Hume pointed out, this justification uses circular 
   reasoning, justifying induction by an appeal that 
   requires induction to gain any force.

The problem of justifying induction remains with us. Hume 
seems to hold the view that we (as well as other animals) 
have an instinct-like belief that the future will resemble 
the past based on the development of habits in our nervous 
system, a belief that we cannot eliminate but which we 
cannot prove true by any kind of argument, deductive or 
inductive, just as is the case with regard to our belief 
in the reality of the external world.

For relevant contemporary work, see Richard Swinburne's 
compilation The Justification of Induction.


The Bundle Theory of the Self

We tend to think that we are the same person we were five 
years ago. Though we've changed in many respects, the same 
person appears present as was present then. We might start 
thinking about which features can be changed without changing 
the underlying self. Hume, however, denies that there is a 
distinction between the various features of a person and the 
mysterious self that supposedly bears those features. After 
all, Hume pointed out, when you start introspecting, you 
notice a bunch of thoughts and feelings and perceptions and 
such, but you never perceive any substance you could call 
"the self". So as far as we can tell, Hume concludes, there 
is nothing to the self over and above a big, fleeting bundle 
of perceptions. Note in particular that, on Hume's view, 
these perceptions do not belong to anything. Rather, Hume 
compares the soul to a commonwealth, which retains its identity 
not by virtue of some enduring core substance, but by being 
composed of many different, related, and yet constantly changing 
elements. The question of personal identity then becomes a 
matter of characterizing the loose cohesion of one's personal 
experience. (Note that in the Appendix to the Treatise, Hume 
said mysteriously that he was dissatisfied with his account 
of the self, and yet he never returned to the issue!)

For relevant contemporary work, see Derek Parfit's Reasons 
and Persons.


Practical Reason: Instrumentalism and Nihilism

Most of us find some behaviors more reasonable than others. 
Eating aluminum foil, for example, seems to have something 
unreasonable about it. But Hume denied that reason has any 
important role in motivating or discouraging behavior. After 
all, reason is just a sort of calculator of concepts and 
experience. What ultimately matters, Hume said, is how we 
feel about the behavior. His work begat the doctrine of 
instrumentalism, which states that an action is reasonable 
if and only if it serves the agent's goals and desires, 
whatever they be. Reason can enter the picture only as a 
lackey, informing the agent of useful facts concerning which 
actions will serve his goals and desires, but never deigning 
to tell the agent which goals and desires he should have. So, 
if you want to eat aluminum foil, reason will tell you where 
to find the stuff, and there's nothing unreasonable about 
eating it or even wanting to do so.

Instrumentalism went on to become the orthodox view of practical 
reason in economics, rational choice theory, and some other 
social sciences. But, some commentators argue, Hume actually 
went a step further to nihilism and said there's nothing 
unreasonable about deliberately frustrating your own goals 
and desires ("I want to eat aluminum foil, so let me wire my 
mouth shut"). Such behavior would surely be highly irregular, 
granting reason no role at all, but it would not be contrary 
to reason, which is impotent to make judgments in this domain.

For relevant contemporary work, see Jean Hampton's The Authority 
of Reason and David Schmidtz's Rational Choice and Moral Agency.


Moral Anti-realism and Motivation

Drawing on his attack on reason's role in judging behavior, 
Hume argues that immoral behavior is not immoral by being 
against reason. He first claims that moral beliefs are 
intrinsically motivating – if you believe killing is wrong, you 
will be ipso facto motivated not to kill and to criticize 
killing and so on (moral internalism). He then reminds us that 
reason alone can motivate nothing – reason discovers matters 
of fact and logic, and it depends on our desires and 
preferences whether apprehension of those truths will motivate 
us. Consequently, reason alone cannot yield moral beliefs. 
Hume proposed that morality ultimately rests upon sentiment, 
with reason only paving the way for our sensitive judgments 
by analysis of the moral matter in question. This argument 
against founding morality on reason is now one in the stable 
of moral anti-realist arguments; Humean philosopher John 
Mackie argued that, for moral facts to be real facts about 
the world and, at the same time, intrinsically motivating, they 
would have to be very weird facts. So we have every reason to 
disbelieve in them.

For relevant contemporary work, see J. L. Mackie's Ethics: 
Inventing Right and Wrong, Mackie's Hume's Moral Theory, 
David Brink's Moral Realism and the Foundation of Ethics, 
and Michael Smith's The Moral Problem.


Free Will versus Indeterminism

Just about everyone has noticed the apparent conflict between 
free will and determinism – if your actions were determined 
to happen billions of years ago, then how can they be up to 
you? But Hume noted another conflict, one that turned the problem 
of free will into a full-fledged dilemma: free will is incompatible 
with indeterminism. Imagine that your actions are not determined by 
what events came before. Then your actions are, it seems, completely 
random. Moreover, and most importantly for Hume, they are not 
determined by your character – your desires, your preferences, your 
values, etc. How can we hold someone responsible for an action that 
did not result from his character? How can we hold someone responsible 
for an action that randomly occurred? Free will seems to require 
determinism, because otherwise, the agent and the action wouldn't 
be connected in the way required of freely chosen actions. So now, 
nearly everyone believes in free will, free will seems inconsistent 
with determinism, and free will seems to require determinism. Hume's 
view is that human behavior, like everything else, is caused, and 
therefore holding people responsible for their actions should focus 
on rewarding them or punishing them in such a way that they will try 
to do what is morally desirable and will try to avoid doing what is 
morally reprehensible. (See also Compatibilism.)

For a relevant contemporary work, see Daniel C. Dennett's Freedom 
Evolves.


The is-ought problem

Hume noted that many writers talk about what ought to be on the 
basis of statements about what is. But there seems to be a big 
difference between descriptive statements (what is) and prescriptive 
statements (what ought to be). Hume calls for writers to be on their 
guard against changing the subject like that, not without giving an 
explanation of how the ought-statements are supposed to follow from 
the is-statements. But how exactly can you derive an 'ought' from 
an 'is'? That question, prompted by Hume's small paragraph, has become 
one of the central questions of ethical theory, and Hume is usually 
assigned the position that such a derivation is impossible. (Others 
interpret Hume as saying not that one cannot go from a factual 
statement to an ethical statement, but that one cannot do so without 
going through human nature, that is, without paying attention to human 
sentiments.) G. E. Moore defended a similar position with his "open 
question argument", intended to refute any identification of moral 
properties with natural properties—the so-called "naturalistic 
fallacy".


Utilitarianism

It was probably Hume who, along with his fellow members of the Scottish 
Enlightenment, first advanced the idea that the explanation of moral 
principles is to be sought in the utility they tend to promote. Hume's 
role is not to be overstated, of course; it was his countryman Francis 
Hutcheson who coined the utilitarian slogan "greatest happiness for the 
greatest numbers". But it was from reading Hume's Treatise that Jeremy 
Bentham first felt the force of a utilitarian system: he "felt as if 
scales had fallen from [his] eyes". Nevertheless, Hume's 
proto-utilitarianism is a peculiar one from our perspective. He doesn't 
think that the aggregation of cardinal units of utility provides a 
formula for arriving at moral truth. On the contrary, Hume was a moral 
sentimentalist and, as such, thought that moral principles could not 
be intellectually justified. Some principles simply appeal to us and 
others don't; and the reason why utilitarian moral principles do 
appeal to us is that they promote our interests and those of our 
fellows, with whom we sympathize. Humans are hard-wired to approve of 
things that help society – public utility. Hume used this insight to 
explain how we evaluate a wide array of phenomena, ranging from social 
institutions and government policies to character traits and talents.


The Problem of Miracles

One way to support a religion is by appeal to miracles. But Hume argued 
that, at minimum, miracles could never give religion much support. There 
are several arguments suggested by Hume's essay, all of which turn on 
his conception of a miracle: namely, a violation of the laws of nature 
by God. One argument claims that it's impossible to violate the laws of 
nature. Another claims that human testimony could never be reliable 
enough to countermand the evidence we have for the laws of nature. The 
weakest and most defensible claims that, due to the strong evidence we 
have for the laws of nature, any miracle claim is in trouble from the 
get-go, and needs strong supporting evidence to defeat our initial 
presumptions. In a slogan, extraordinary claims require extraordinary 
evidence. This point has been most applied to the question of the 
resurrection of Jesus, where Hume would no doubt ask, "Which is more 
likely – that a man rose from the dead or that this testimony is 
mistaken in some way?" Or, more blandly, "Which is more likely – that 
Uri Geller can really bend spoons with his mind or that there is 
some trick going on?" This argument is the backbone of the sceptic's 
movement and a live issue for historians of religion. For a critical 
and technical (Bayesian) analysis of Hume, see John Earman's Hume's 
Abject Failure – the title of which gives you an idea of his 
assessment. For a rebuttal of Earman's interpretation of Hume, 
see Robert Fogelin's A Defense of Hume on Miracles.


The Design Argument

One of the oldest and most popular arguments for the existence of 
God is the design argument – that all the order and 'purpose' in the 
world bespeaks a divine origin. Hume gave the classic criticism of 
the design argument, and though the issue is far from dead, many are 
convinced that Hume killed the argument for good. Here are some of 
his points:

   1. For the design argument to work, it needs to be true that 
   about the only time we see order and perceived purpose is 
   when it results from design. But we see order all the time, 
   resulting from presumably mindless processes like generation 
   and vegetation. Design accounts for only a tiny part of our 
   experience with order and "purpose".
   2. Supposing the design argument worked, it could not (in of 
   itself) support a robust theism; one could easily reach the 
   conclusion that the universe's configuration is the result of 
   some morally ambiguous, possibly unintelligent agent or agents 
   whose method bears a remote similarity to human design.
   3. For the design argument to reach its logical conclusion, 
   God's mental order and functioning needs explanation, as we 
   could otherwise leave the universe's order, etc unexplained.
   4. Often, what appears to be purpose, where it looks like 
   object X has feature F in order to secure some outcome O, 
   is better explained by a filtering process: that is, object 
   X wouldn't be around did it not possess feature F, and 
   outcome O is only interesting to us, a human projection of 
   goals onto nature. This mechanical explanation of teleology 
   anticipated natural selection.

For relevant contemporary work, see J. C. A. Gaskin's Hume's 
Philosophy of Religion, and Richard Swinburne's The Existence 
of God; for a view from a philosopher of biology, see Elliott 
Sober's Philosophy of Biology, ch. 2.



Conservatism and Political Theory

Many regard David Hume as a political conservative, sometimes 
calling him the first conservative philosopher. He expressed 
suspicion of attempts to reform society in ways that departed 
from long-established custom, and he counselled people not 
to resist their governments except in cases of the most 
egregious tyranny. However, he resisted aligning himself with 
either of Britain's two political parties, the Whigs and the 
Tories, and he believes that we should try to balance our 
demands for liberty with the need for strong authority, 
without sacrificing either. He supported liberty of the 
press, and was sympathetic to democracy, when suitably 
constrained. It has been argued that he was a major inspiration 
for James Madison's writings, and the Tenth Federalist in 
particular. He was also, in general, an optimist about social 
progress, believing that, thanks to the economic development 
that comes with the expansion of trade, societies progress 
from a state of "barbarism" to one of "civilization". 
Civilized societies are open, peaceful and sociable, and their 
citizens are as a result much happier. It is therefore not 
fair to characterise him, as Leslie Stephen did, as favouring 
"that stagnation which is the natural ideal of a sceptic". 
(Leslie Stephen, History of English Thought in the Eighteenth 
Century, 2 vols. (London: Smith, Elder and Co., 1876), vol. 
2, 185.)

For more, see Douglas Adair's "That Politics May Be Reduced 
to a Science: David Hume, James Madison and the Tenth 
Federalist" in Fame and the Founding Fathers; Donald W 
Livingston, Hume's Philosophy of Common Life; John B Stewart,
Opinion and Reform in Hume's Political Philosophy.


Works

    * A Treatise of Human Nature: Being an Attempt to introduce 
    the experimental Method of Reasoning into Moral Subjects. 
    (1739–40)
          o Book 1: "Of the Understanding" His treatment of 
          everything from the origin of our ideas to how they 
          are to be divided. Important statements of Scepticism.
          o Book 2: "Of the Passions" Treatment of emotions.
          o Book 3: "Of Morals" Moral ideas, justice, obligations, 
          benevolence.

    Hume intended to see whether the Treatise met with success, 
    and if so to complete it with books devoted to Politics and 
    Criticism. (It did not meet with success, and so was not 
    completed.)

    * An Enquiry Concerning Human Understanding (1748)

    Contains reworking of the main points of the Treatise, Book 
    1, with the addition of material on free will, miracles, and 
    the argument from design.

    * An Enquiry Concerning the Principles of Morals (1751)

    Another reworking of material from the Treatise for more 
    popular appeal. Hume regarded this as the best of all his 
    philosophical works, both in its philosophical ideas and 
    in its literary style.

    * Dialogues Concerning Natural Religion (posthumous)

    Discussions between fictional characters Cleanthes, Philo, 
    and Demea. They discuss proofs of the existence of God and 
    other fun stuff. Although there's some controversy, most 
    scholars agree that Philo's view comes closest to Hume's 
    own.

    * Essays Moral and Political (first ed. 1741–2)

    A collection of pieces written over many years and 
    published in a series of volumes before being gathered 
    together into one near the end of Hume's life. The essays 
    are dizzying and even bewildering in the breadth of topics 
    they address. They range freely over questions of 
    aesthetic judgement, the nature of the British government, 
    love, marriage and polygamy, and the demographics of ancient 
    Greece and Rome, to name just a few of the topics considered. 
    However, certain important topics and themes recur, especially 
    the question of what constitutes "refinement" in matters of 
    taste, manners and morals. The Essays are written in clear 
    imitation of the Tatler and the Spectator, which Hume read 
    avidly in his youth.

    * The History of England (1754–62)

    This forms more a category of books than a single work, a 
    monumental history spanning "from the invasion of Julius 
    Caesar to the Revolution of 1688". This work brought Hume 
    the most fame during his own lifetime, going through over 
    100 editions. Many considered it the standard history of 
    England until the publication of Thomas Macaulay's own 
    monumental History of England.