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.

[26] Hume was derailed in his attempts to start a university career by protests over his alleged "atheism",[27][28] also lamenting that his literary debut, A Treatise of Human Nature, "fell dead-born from the press.

[31] As Hume had spent most of his savings during those four years,[21] he resolved "to make a very rigid frugality supply [his] deficiency of fortune, to maintain unimpaired [his] independency, and to regard every object as contemptible except the improvements of [his] talents in literature".

[40] By the end of this period Hume had attained his well-known corpulent stature; "the good table of the General and the prolonged inactive life had done their work", leaving him "a man of tremendous bulk".

[53] In June of that year, Hume facilitated the purchase of a slave plantation in Martinique on behalf of his friend, the wine merchant John Stewart, by writing to the colony's governor Victor-Thérèse Charpentier.

Hume also provides an unambiguous self-assessment of the relative value of his works: that "my Enquiry concerning the Principles of Morals; which, in my own opinion (who ought not to judge on that subject) is of all my writings, historical, philosophical, or literary, incomparably the best."

Adam Smith later recounted Hume's amusing speculation that he might ask Charon, Hades' ferryman, to allow him a few more years of life in order to see "the downfall of some of the prevailing systems of superstition".

[73] Controversially, Hume, in some sense, may regard the distinction as a matter of degree, as he takes impressions to be distinguished from ideas on the basis of their force, liveliness, and vivacity—what Henry E. Allison (2008) calls the "FLV criterion.

Regardless of how boundless it may seem; a person's imagination is confined to the mind's ability to recombine the information it has already acquired from the body's sensory experience (the ideas that have been derived from impressions).

[80] Hume argues that we tend to believe that things behave in a regular manner, meaning that patterns in the behaviour of objects seem to persist into the future, and throughout the unobserved present.

He split causation into two realms: "All the objects of human reason or enquiry may naturally be divided into two kinds, to wit, Relations of Ideas, and Matters of Fact.

[ii] Hume said that, when two events are causally conjoined, a necessary connection underpins the conjunction:[91] Shall we rest contented with these two relations of contiguity and succession, as affording a complete idea of causation?

Simon Blackburn calls this a quasi-realist reading,[94] saying that "Someone talking of cause is voicing a distinct mental set: he is by no means in the same state as someone merely describing regular sequences.

When my perceptions are removed for any time, as by sound sleep; so long I am insensible of myself, and may truly be said not to exist.This view is supported by, for example, positivist interpreters, who have seen Hume as suggesting that terms such as "self", "person", or "mind" refer to collections of "sense-contents".

Corliss Swain notes that "Commentators agree that if Hume did find some new problem" when he reviewed the section on personal identity, "he wasn't forthcoming about its nature in the Appendix.

[133] Education writer Richard Wright considers that Hume's position rejects a famous moral puzzle attributed to French philosopher Jean Buridan.

[135][136] Philosopher Paul Russell (2005) contends that Hume wrote "on almost every central question in the philosophy of religion", and that these writings "are among the most important and influential contributions on this topic.

He adds that Hume "did not believe in the God of standard theism ... but he did not rule out all concepts of deity", and that "ambiguity suited his purposes, and this creates difficulty in definitively pinning down his final position on religion".

[1] A century later, the idea of order without design was rendered more plausible by Charles Darwin's discovery that the adaptations of the forms of life result from the natural selection of inherited characteristics.

In his Dialogues Concerning Natural Religion, Hume wrote:[155] Many worlds might have been botched and bungled throughout an eternity, ere this system was struck out: much labour lost: many fruitless trials made: and a slow, but continued improvement carried on during infinite ages in the art of world-making.

[157] In An Enquiry Concerning Human Understanding (Section 10), Hume defines a miracle as "a transgression of a law of nature by a particular volition of the Deity, or by the interposition of some invisible agent".

In all cases, we must balance the opposite experiments ... and deduct the smaller number from the greater, in order to know the exact force of the superior evidence.Hume discusses the testimony of those who report miracles.

By Hume's lights, this refusal is not wrong and the prince "reasoned justly;" it is presumably only when he has had extensive experience of the freezing of water that he has warrant to believe that the event could occur.

He makes an ironic remark that anyone who "is moved by faith to assent" to revealed testimony "is conscious of a continued miracle in his own person, which subverts all principles of his understanding, and gives him a determination to believe what is most contrary to custom and experience.

[191] The legacy of religious civil war in 18th-century Scotland, combined with the relatively recent memory of the 1715 and 1745 Jacobite risings, had fostered in Hume a distaste for enthusiasm and factionalism.

"[193] Hume expressed suspicion of attempts to reform society in ways that departed from long-established custom, and he counselled peoples not to resist their governments except in cases of the most egregious tyranny.

McArthur characterises Hume as a "precautionary conservative,"[197]: 124  whose actions would have been "determined by prudential concerns about the consequences of change, which often demand we ignore our own principles about what is ideal or even legitimate.

He hoped that "in some future age, an opportunity might be afforded of reducing the theory to practice, either by a dissolution of some old government, or by the combination of men to form a new one, in some distant part of the world".

[199] Political philosophers Leo Strauss and Joseph Cropsey, writing of Hume's thoughts about "the wise statesman", note that he "will bear a reverence to what carries the marks of age."

[217][218] Hume pioneered a comparative history of religion,[219][220] tried to explain various rites and traditions as being based on deception[221][222] and challenged various aspects of rational and natural theology, such as the argument from design.