| Thinking hard, or|
|Major trains of thought|
|The good, the bad|
and the brain fart
|Come to think of it|
|—David Hume, as recounted by Lord Henry Brougham|
 Conception of the self
Hume did not believe in a unified and continuous "self"; rather he believed that the self is an illusion generated through a chain of perceptions that result in a feeling of personal identity.
Hume was considered to be an atheist by many of his contemporaries, but exactly how much of an atheist he was is debated. The consensus seems to be that he was at least irreligious though he did not reject the possibility of a God as some of his contemporary atheist philosophers did — bringing him closer into agnostic levels. He proposed instead we should be skeptical of the claims made by any religions, and that most modern religions were continuations of ancient religions created by people who proposed invisible agents that did not in fact exist. His atheism became an issue throughout his life as he was denied opportunities and even charged with heresy, a charge he beat when his clerical friends came to his defense by declaring, ironically, he couldn't be a heretic because he wasn't a Christian.
 Hume's law
One of his most famous proposals is the is-ought problem, which states that you cannot derive an "ought" from an "is." That is to say, you cannot go from some truth value about what "is" true, to saying what you "ought" to do or what "ought" to be true. To bridge the gap you must propose and then defend an additional ethical principle.
For instance, it is not enough to say, "Eating fruit is healthy, therefore you ought to eat fruit." You must also add something so it appears like, "Eating fruit is healthy, and if you want to be healthy then you ought to eat fruit," or, "Eating fruit is healthy and you should be healthy therefore you ought to eat fruit." Notice that both of these additions now make the assumption that you should be or want to be healthy, and if you agree with this it is a more convincing argument. It does, however, also give more to defend, as you may be forced to justify why you should want to be healthy.
 The problem of induction and causal skepticism
Hume was one of the most famous skeptics of induction and causality. Hume starts with his distinction between "matters of fact" and "relations of ideas" and his empiricist ideas about how humans reason. Hume claims that we gather knowledge about the world through the senses, so, psychologically speaking, we are reliant on inductive reasoning. However, he questions whether this knowledge can be truly justified because he sees induction itself as logically unjustifiable. Induction cannot be justified through deductive reasoning because the latter consists merely of relations of ideas, i.e. ones that are true by definition. Induction also cannot be justified inductively, because that would be circular reasoning. Thus, Hume concludes, we unjustifiably attempt to predict the future from past events. Perhaps the most famous illustration of the problem of induction was given not by Hume, but by Bertrand Russell. Russell imagines a chicken on a farm. The farmer feeds it every day, so the chicken assumes that this will continue indefinitely. One day, though, the chicken has its neck wrung and is killed.
The problem of induction leads Hume to be a skeptic about causality:
- If induction cannot be justified, we can't definitively make statements about causality. According to Hume, we have no direct access to knowledge about causality.
- We can only observe regularities in the natural world. That is, we only think that event X causes event Y because we always see Y following X. But...
- If induction is not justified, then we have no reason to assume that nature is uniform. The only reason we have to make this causal connection is because we have always seen Y come after X.
There is a hard and a soft interpretation of Hume's view on causality; the harder, metaphysical interpretation states that causality itself does not exist. The softer, epistemological interpretation states that causality may exist, but we have no justification for believing it.
 See also
- ↑ 1.0 1.1 David Hume (1711-1776) Internet Encyclopedia of Philosophy
- ↑ 2.0 2.1 David Hume Stanford Encyclopedia of Philosophy.
- ↑ The Riddle of Hume's Treatise: Skepticism, Naturalism, and Irreligion, University of Notre Dame.
- ↑ Hume's Agnosticism, The Philosophical Review
- ↑ The Enlightenment, Edinburgh City Mission
- ↑ Bertrand Russell. "On Induction", Chapter VI in The Problems of Philosophy (1912).
- ↑ For more, see the SEP entry on the Problem of Induction and the IEP entry, David Hume: Causation.