Unless some foundation was given for this impression by the theological writers whose works had fallen in Hume's way, it is difficult to account for the depth of feeling which so good natured a man manifests on the subject.
Thus he writes in the Natural History of Religion, with quite unusual acerbity:—
"The chief objection to it [the ancient heathen mythology] with regard to this planet is, that it is not ascertained by any just reason or authority. The ancient tradition insisted on by heathen priests and theologers is but a weak foundation: and transmitted also such a number of contradictory reports, supported all of them by equal authority, that it became absolutely impossible to fix a preference among them. A few volumes, therefore, must contain all the polemical writings of pagan priests: And their whole theology must consist more of traditional stories and superstitious practices than of philosophical argument and controversy.
"But where theism forms the fundamental principle of any popular religion, that tenet is so conformable to sound reason, that philosophy is apt to incorporate itself with such a system of theology. And if the other dogmas of that system be contained in a sacred book, such as the Alcoran, or be determined by any visible authority, like that of the Roman pontiff, speculative reasoners naturally carry on their assent, and embrace a theory, which has been instilled into them by their earliest education, and which also possesses some degree of consistence and uniformity. But as these appearances are sure, all of them, to prove deceitful, philosophy will very soon find herself very unequally yoked with her new associate; and instead of regulating each principle, as they advance together, she is at every turn perverted to serve the purposes of superstition. For besides the unavoidable incoherences, which must be reconciled and adjusted, one may safely affirm, that all popular theology, especially the scholastic, has a kind of appetite for absurdity and contradiction. If that theology went not beyond reason and common sense, her doctrines would appear too easy and familiar. Amazement must of necessity be raised: Mystery affected: Darkness and obscurity sought after: And a foundation of merit afforded to the devout votaries, who desire an opportunity of subduing their rebellious reason by the belief of the most unintelligible sophisms.
"Ecclesiastical history sufficiently confirms these reflections. When a controversy is started, some people always pretend with certainty to foretell the issue. Whichever opinion, say they, is most contrary to plain reason is sure to prevail; even when the general interest of the system requires not that decision. Though the reproach of heresy may, for some time, be bandied about among the disputants, it always rests at last on the side of reason. Any one, it is pretended, that has but learning enough of this kind to know the definition of Arian, Pelagian, Erastian, Socinian, Sabellian, Eutychian, Nestorian, Monothelite, &c., not to mention Protestant, whose fate is yet uncertain, will be convinced of the truth of this observation. It is thus a system becomes absurd in the end, merely from its being reasonable and philosophical in the beginning.
"To oppose the torrent of scholastic religion by such feeble maxims as these, that it is impossible for the same thing to be and not to be, that the whole is greater than a part, that two and three make five, is pretending to stop the ocean with a bulrush. Will you set up profane reason against sacred mystery? No punishment is great enough for your impiety. And the same fires which were kindled for heretics will serve also for the destruction of philosophers."—(IV. pp. 481-3.)
Holding these opinions respecting the recognised systems of theology and their professors, Hume, nevertheless, seems to have had a theology of his own; that is to say, he seems to have thought (though, as will appear, it is needful for an expositor of his opinions to speak very guardedly on this point) that the problem of theism is susceptible of scientific treatment, with something more than a negative result. His opinions are to be gathered from the eleventh section of the Inquiry (1748); from the Dialogues concerning Natural Religion, which were written at least as early as 1751, though not published till after his death; and from the Natural History of Religion, published in 1757.
In the first two pieces, the reader is left to judge for himself which interlocutor in the dialogue represents the thoughts of the author; but, for the views put forward in the last, Hume accepts the responsibility. Unfortunately, this essay deals almost wholly with the historical development of theological ideas; and, on the question of the philosophical foundation of theology, does little more than express the writer's contentment with the argument from design.
"The whole frame of nature bespeaks an Intelligent Author; and no rational inquirer can, after serious reflection, suspend his belief a moment with regard to the primary principles of genuine Theism and Religion.—(IV. p. 435.)
"Were men led into the apprehension of invisible, intelligent power, by a contemplation of the works of nature, they could never possibly entertain any conception but of one single being, who bestowed existence and order on this vast machine, and adjusted all its parts according to one regular plan or connected system. For though, to persons of a certain turn of mind, it may not appear altogether absurd, that several independent beings, endowed with superior wisdom, might conspire in the contrivance and execution of one regular plan, yet is this a merely arbitrary supposition, which, even if allowed possible, must be confessed neither to be supported by probability nor necessity. All things in the universe are evidently of a piece. Everything is adjusted to everything. One design prevails throughout the whole. And this uniformity leads the mind to acknowledge one author; because the conception of different authors, without any distinction of attributes or operations, serves only to give perplexity to the imagination, without bestowing any satisfaction on the understanding."—(IV. p. 442.)
Thus Hume appears to have sincerely accepted the two fundamental conclusions of the argument from design; firstly, that a Deity exists; and, secondly, that He possesses attributes more or less allied to those of human intelligence. But, at this embryonic stage of theology, Hume's progress is arrested; and, after a survey of the development of dogma, his "general corollary" is, that—
"The whole is a riddle, an enigma, an inexplicable mystery. Doubt, uncertainty, suspense of judgment, appear the only result of our most accurate scrutiny concerning this subject. But such is the frailty of human reason, and such the irresistible contagion of opinion, that even this deliberate doubt could scarcely be upheld; did we not enlarge our view, and opposing one species of superstition to another, set them a quarrelling; while we ourselves, during their fury and contention, happily make our escape into the calm, though obscure, regions of philosophy."—(IV. p. 513.)
Thus it may be fairly presumed that Hume expresses his own sentiments in the words of the speech with which Philo concludes the Dialogues.
"If the whole of natural theology, as some people seem to maintain, resolves itself into one simple, though somewhat ambiguous, at least undefined proposition, That the cause or causes of order in the universe probably bear some remote analogy to human intelligence: If this proposition be not capable of extension, variation, or more particular explication: If it affords no inference that affects human life or can be the source of any action or forbearance: And if the analogy, imperfect as it is, can be carried no further than to the human intelligence, and cannot be transferred, with any appearance of probability, to the other qualities of the mind; if this really be the case, what can the most inquisitive, contemplative, and religious man do more than give a plain, philosophical assent to the proposition, as often as it occurs, and believe that the arguments on which it is established exceed the objections which lie against it? Some astonishment indeed will naturally arise from the greatness of the object; some melancholy from its obscurity; some contempt of human reason, that it can give no solution more satisfactory with regard to so extraordinary and magnificent a question. But believe me, Cleanthes, the most natural sentiment which a well-disposed mind will feel on this occasion, is a longing desire and expectation that Heaven would be pleased to dissipate, at least alleviate, this profound ignorance, by affording some more particular revelation to mankind, and making discoveries of the nature, attributes, and operations of the Divine object of our faith."[29]—(II. pp. 547-8.)