Religious Philosophers and Speculative Atheists
Interpretations of Hume's philosophy of religion are often made against the background of more general interpretations of his philosophical intentions. From this perspective, it is not unusual to view Hume's views on religion in terms of the skepticism and naturalism that features prominently in his Treatise of Human Nature (1739-40), his first and most ambitious philosophical work. According to the account that is now widely accepted in the scholarly literature, Hume removed almost all the material in the Treatise that was concerned with religion because he was anxious to avoid causing any “offence” among the orthodox. In his later works, beginning with an Enquiry Concerning Human Understanding (1748), Hume began to present his views on this subject in a more substantial and direct manner. This culminates in his Natural History of Religion (1757) and Dialogues Concerning Natural Religion (1779; published posthumously) – both of which are entirely taken up with philosophical issues in religion. The linkage between these various works, on this account, is that the later writings on religion are simply an extension and application of the sceptical and naturalistic principles that Hume developed in his earlier writings.

While it is certainly true that there is an intimate connection between Hume's scepticism and naturalism and his irreligious objectives and orientation, it is not evident that this relationship should be understood in terms of Hume drawing irreligious consequences in his later work from the sceptical and naturalistic principles that he laid down in his earlier work. There is a more intimate connection between these components of Hume's philosophy than this account suggests. Apart from any thing else, the traditional account seriously underestimates the irreligious content and aims of Hume's earlier work - particularly in the Treatise. Moreover, a view of this kind is liable to overlook the way in which 17th and 18th century theological controversies and debates structure and shape Hume's entire philosophy — not just his philosophy of religion. Put another way, Hume's philosophy of religion is integral to his entire philosophical system. It should not be viewed as an extraneous outgrowth or extension of earlier concerns and commitments that lack any specific irreligious motivation or orientation.

In the opening paragraph of the last section of the first Enquiry (XII) Hume makes the following observation:

There is not a greater number of philosophical reasonings, displayed upon any subject, than those, which prove the existence of a Deity, and refute the fallacies of Atheists; and yet the most religious philosophers still dispute whether any man can be so blinded as to be a speculative atheist. (EU.149/12.1 — Hume's emphasis)
These remarks bring to light an important point. The central debate that shapes Hume's views on the subject of religion is not the empiricist/rationalist controversy, nor its “British”/”continental” correlate, but a more fundamental dispute between philosophical defenders of Christian theology and their “atheistic” opponents. It is this divide over issues of religion that is especially important for understanding the positions and arguments that Hume presents throughout his philosophical writings.

During the 17th and early 18th centuries British philosophy gave rise to two powerful but conflicting philosophical outlooks. On one hand, this era has been described as “the golden period of English theology” because of the emerging alliance between philosophy and theology. It was, in particular, a major concern of a number of divines at this time to show that theology could be provided with a rational defence — one that would ward off all threat of scepticism and atheism. Among the leading representatives of this tradition were Henry More, Ralph Cudworth, John Locke, Samuel Clarke, George Berkeley and Joseph Butler. (More and Cudworth were both Cambridge Platonists.) On the other hand, in opposition to this Christian tradition, there existed a sceptical tradition of which the greatest representative was Thomas Hobbes. Almost all the defenders of the Christian religion during this period had their arguments targeted against the “atheistic” doctrines of Hobbes.

From the perspective of Hobbes's critics the doctrines that lay at the heart of his atheism were materialism, necessitarianism, moral relativism and egoism, and scepticism concerning natural and revealed religion. Any thinker who endorsed doctrines of this kind was liable to be read as a follower of Hobbes and branded an “atheist”. During this period Hobbes was not without his followers. The most important thinker to become closely associated with Hobbes, in the minds of his critics, was Benedict Spinoza. In the Theological-Political Treatise (1670) Spinoza pursued a number of Hobbesean themes, including biblical criticism, scepticism about miracles and strong anti-clericalism. Spinoza's Ethics (1677) was also identified as containing Hobbist doctrines (e.g., materialism and necessitarianism) that led directly to atheism. Given these points of resemblance, Hobbes's critics in England were quick to link the names of Hobbes and Spinoza and they viewed “Spinozism” as simply a variant of the prevalent disease of “Hobbist atheism”.

Another important source of “atheistic” or irreligious thought during this period was the sceptical philosophy of Pyrrho, as presented in the writings of Sextus Empiricus. Pierre Bayle describes the significance of Pyrrhonianism in his influential Historical and Critical Dictionary (1702), a work that we know was read carefully by the young Hume. In his article on “Pyrrho” Bayle argues:

Pyrrhonism is dangerous in relation to this divine science [theology], but it hardly seems so with regard to the natural sciences or to the state… Society has no reason to be afraid of scepticism; for sceptics do not deny that one should conform to the customs of one's country, practice one's moral duties, and act upon matters on the basis of probabilities without waiting for certainty… It is therefore only religion that has anything to fear from Pyrrhonism. Religion ought to be based on certainty. Its aim, its effects, its usages collapse as soon as this firm conviction of its truth is erased from the human mind. (Bayle, Dictionary, art. “Pyrrho”, Note B; p. 195)
Bayle's own view that philosophy and theology should be sharply separated, on the ground that the doctrines of theology could not be defended by reason and were therefore a matter of faith alone, brought his work under the suspicion of atheism. In general, it was common among Hume's immediate predecessors and contemporaries to associate scepticism closely with atheism. (Hume's writings allude to this at various points. See, e.g., Hume's “Early Memoranda”, Sect. II, #40)

A significant development in the late 17th century relating to the war against the atheism of Hobbes and his followers was the establishment of the Boyle Lectures. These lectures were founded by Robert Boyle, the distinguished scientist, for the purpose of “proving the Christian, against notorious Infidels, viz. Atheists, Theists, Pagans…” By the early 18th century the Boyle lectures had become the focus for the debate between the Newtonians (the intellectual heirs of Hobbes's early critics) and the radical freethinkers, who followed in the tradition of Hobbes and Spinoza. The greatest and most influential of the Boyle lecturers was Samuel Clarke, who was a close friend of Newton's and widely recognized as the most able defender of Newtonian philosophy and theology. Clarke's Boyle lectures were published in 1704 as A Demonstration of the Being and Attributes of God. The center-piece of this work is Clarke's version of the cosmological argument or argument a priori. John Locke presented a similar version of this argument in his Essay Concerning Human Understanding (1690). What Locke and Clarke were agreed about was that it is possible to demonstrate the existence of God — just as it is possible to demonstrate truths in mathematics. Clarke's statement of the argument a priori enjoyed considerable prestige throughout the first half of the 18th century and found strong support among several Scottish philosophers of considerable reputation at this time (e.g., Andrew Baxter). There was, nevertheless, another very different approach - well established within latitudinarian and Newtonian theological circles - for proving the existence of God. This was the argument from design or argument a posteriori (also known as teleological arguments). Among the most prominent champions of this form of argument during the early 18th century were the Scottish Newtonians George Cheyne and Colin Maclaurin. It is these two proofs for the existence of God — i.e., the arguments a priori and a posteriori – that Hume's philosophical writings are particularly concerned with and seek to discredit.

Although the British debate between “religious philosophers” and “speculative atheists” is especially important for understanding Hume's own arguments and positions concerning religion it would be a mistake to overlook the contribution of continental thinkers to this debate. One thinker who is of considerable importance in this regard is Rene Descartes. In his Meditations (1641) Descartes, famously, attempts to prove the existence of God by means of two rationalistic arguments, both of which proceed from our innate idea of God. The first argument, presented in his third Meditation, proceeds by way of claiming that the causal origins of this idea must be accounted for in terms of an actually existing perfect being (as no other cause is adequate to produce this effect). In Descartes's fifth Meditation he presents his own version of the ontological argument. Here he argues that God's actual existence is logically implied by our idea of God as a perfect being. According to this argument, it would be as contradictory to say that we have an idea of God but deny that he exists as it would be to say we have an idea of a triangle that does not have three sides. This argument has the same general objective as the cosmological argument that Locke and Clarke advanced: it aims to prove the necessary existence of God.

Finally, it should also be noted that Hume's Scottish contemporaries were heavily involved in the general debate between “religious philosophers” and “speculative atheists”. This includes a number of significant and influential thinkers with whom Hume likely came into contact while he was a student at Edinburgh University in the 1720's (e.g., Colin Maclaurin). Beyond this, it also includes several philosophers who were active in the Borders area of Scotland when Hume was living there as a young man and still in the early stages of his philosophical development (e.g. Andrew Baxter, Henry Home [Lord Kames]). In Hume's own lifetime his philosophy was widely regarded — in both Scotland and England - as being “atheistic” in character and generally hostile to religion. What is particularly significant, however, is that this way of viewing Hume's philosophy was not generated by the Dialogues — since it was published posthumously – but by his earlier philosophical work. This certainly includes the Treatise, which our own contemporaries tend to regard as having little or no relevance for problems of religion.