The version in Part XI can be expressed as follows:
There are four major causes of natural evil in the world:
1. Pleasure and pain as the mechanisms of species preservation: Why pain? Prima facie, the same end could be achieved by via the mechanisms of pleasure and its diminishment in the appropriate circumstances.[1]
2. Laws of Nature: Granted, humans and the other animals might well need the world to exhibit a fairly high degree of regularity for a recognizable and decent life, and natural laws provide such regularity. But prima facie, the requisite degree of regularity is compatible with God's frequent direct intervention in the world to prevent apparently gratuitous suffering and enable flourishing. And prima facie, it would’ve been much better for humans and animals if God frequently intervened in nature to achieve such ends (perhaps incognito, if that is required to achieve his aims).[2]
3. The frugal distribution of powers and faculties among humans and animals: Relatively few sentient creatures have a quality of life that can be properly characterized as 'flourishing'. In fact, the quality of life for very many sentient creatures scarcely rises above the minimum required for survival and reproduction. Indeed, most creatures languish for at least a significant portion of their lives. The presence of an advantageous ability in a human or an animal is almost always offset by the lack of one or more other abilities that would allow them to flourish. It appears that the bulk of human and animal suffering could be avoided if they were endowed with just a slightly larger variety of traits and abilities -- or even just a slight improvement of those they do have. Prima facie, then, the aims of nature do not include the flourishing of living things, but only their mere propagation and preservation.[3]
4. The flaws in nature’s mechanisms: To the impartial observer, Nature’s mechanisms appear to operate at a level that's far from optimal. Some mechanisms are sub-optimal in the sense that they not infrequently yield too little or too much of their output. So, for example, the mechanisms that give us rain often don’t operate when they should (leading to drought), or operate in excess (leading to flooding). Other forms of sub-optimal function are more invasive. So, for example, the mechanisms responsible for the functioning of cells and other parts often malfunction, leading to cancer, birth defects, and other ills. Thus, if the universe is really God’s machine (as Cleanthes' version of the design argument in Part II of the Dialogues aims to show), and creaturely flourishing is part of its design plan, it appears to be a tragically imperfect and inefficient one.[4]
Call circumstances (1)-(4), “the data”. What hypothesis best explains the data? Hume points out that the hypotheses reduce to four:
H1. The cause(s) of the universe is (are) perfectly good.
H2. The cause(s) of the universe is (are) perfectly evil.
H3. Some of the causes of the universe are good, and some are evil.
H4. The cause(s) of the universe is (are) neither good nor evil. (Paul Draper calls this ‘the hypothesis of indifference’)
Hume argues that hypotheses H1-H3 are explanations for the data that are less than best:
-H1 and H2 are each ruled out as the best explanation, as unmixed causes (either perfect goodness or perfect evil) can't be the best explanation of mixed phenomena (both good and evil).
-H3 is ruled out as the best explanation, as there is too much regularity in the world to suggest a “battle” between good and evil played out in the universe.
In contrast to H1-H3, H4 conforms very well to what we see with respect to data (1)-(4): we would expect such data if the cause(s) of the universe were neither good nor evil, but rather non-moral entities or mechanisms (such as the mechanisms of the natural world studied in the sciences). Therefore, H4 is the best explanation of the data.
To quote Hume: “Look round the universe. What an immense profusion of beings, animated and organized, sensible and active! You admire this prodigious variety and fecundity. But inspect a little more narrowly these living existences, the only things worth regarding. How hostile and destructive to each other! How insufficient all of them for their own happiness! How contemptible or odious to the spectator! The whole presents nothing but the idea of a blind nature, impregnated by a great vivifying principle, and pouring forth from her lap, without discernment or parental care, her maimed and abortive children.”[5]
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Notes:
[1] Hume, David. Dialogues Concerning Natural Religion, J.C.A. Gaskin, ed. (Oxford: Oxford University Press), Part XI, pp. 107-8.
[2] Hume notes that it seems that even relatively infrequent divine intervention would lead to a drastic reduction in the worlds ills. "A few...events..., regularly and wisely distributed, would change the face of the world; and yet would no more seem to disturb the course of nature or confound human conduct, than the present economy of things, where the causes are secret, and variable, and compounded. Some small touches, given to Caligula's brain in his infancy, might have converted him into a Trajan: one wave, a little higher than the rest, by burying Caesar and his fortune in the bottom of the ocean, might have restored liberty to a considerable part of mankind. There may, for aught we know, be good reasons, why providence interposes not in this manner, but they are unknown to us: And though the mere supposition, that such reasons exist, may be sufficient to save the conclusion concerning the divine attributes [i.e., that God is all-knowing, all-powerful, and perfectly good], yet surely it can never be sufficient to establish that conclusion." Ibid, p. 109.
[3] Hume so masterfully illustrates this point that he deserves to be quoted at length: "Every animal has the requisite endowments; but these endowments are bestowed with so scrupulous an economy, that any considerable diminution must entirely destroy the creature. Wherever one power is increased, there is a proportional abatement in the others. Animals, which excel in swiftness, are commonly defective in force. Those, which possess both, are either imperfect in some of their senses, or are oppressed with the most craving wants. The human species, whose chief excellency is reason and sagacity, is of all others the most necessitous, and the most deficient in bodily advantages; without clothes, without arms, without food, without lodging, without any convenience of life, except what they owe to their own skill and industry. In short, nature seems to have formed an exact calculation of the necessities of her creatures; and like a rigid master, has afforded them little more powers or endowments, than what are strictly sufficient to supply those necessities. An indulgent parent would have bestowed a large stock, in order to guard against accidents, and secure the happiness and welfare of the creature, in the most unfortunate concurrence of circumstances. Every course of life would not have been so surrounded with precipices, that the least departure from the true path, by mistake or necessity, must involve us in misery and ruin. Some reserve, some fund would have been provided to ensure happiness; nor would the powers and the necessities have been adjusted with so rigid an economy. The Author of Nature is inconceivably powerful: His force is supposed great, if not altogether inexhaustible: Nor is there any reason, as far as we can judge, to make him observe this strict frugality in his dealings with his creatures...In order to cure most of the ills of human life, I require not that man should have the wings of an eagle, the swiftness of the stag, the force of the ox, the arms of the lion, the scales of the crocodile or rhinoceros; much less do I demand the sagacity of an angel or cherubim. I am contented to take an increase in one single power or faculty of his soul. Let him be endowed with a greater propensity to industry and labour; a more vigorous spring and activity of mind; a more constant bent to business and application. Let the whole species possess naturally an equal diligence with that which many individuals are able to attain by habit and reflection; and the most beneficial consequences, without any allay of ill, is the immediate and necessary result of this endowment. Almost all the moral, as well as the natural evils of human life arise from idleness; and were our species, by the original constitution of their frame, exempt from this vice or infirmity, the perfect cultivation of the land, the improvement of arts and manufactures, the exact execution of every office and duty, immediately follow; and met at once may fully reach that state of society, which is so imperfectly attained by the best-regulated government. But as industry is a power, and the most valuable than any, nature seems determined, suitably to her usual maxims, to bestow it on men with a very sparing hand; and rather to punish him severely for his deficiency in it, than to reward him for his attainments. She has so contrived his frame, that nothing but the most violent necessity can oblige him to labour; and she employs all his other wants to overcome, at least in part, the want of diligence, and to endow him with some share of a faculty, of which she has thought fit to naturally bereave him." Ibid., pp. 110-11.
[4] Ibid., pp. 111-12.
[5] Ibid., p. 113.
