David Hume's influence on Charles Darwin

As a result of helping my son Charlie with his homework, I have just (re-)read David Hume's Dialogues Concerning Natural Religion, which is a superb examination of the arguments for and against the existence of God. 

I was surprised to see how similar some parts of the Dialogues are to some parts of Darwin's own writings. I spent a bit of time Googling away to see if anyone else had noticed this, but can't find much evidence that anyone has. I found this one paper:

• David Hume and Charles Darwin, William B. Huntley, Journal of the History of Ideas, Vol. 33, No. 3, Festschrift for Philip P. Wiener (Jul. - Sep., 1972), pp. 457-470 http://www.jstor.org/stable/2709046
  

But this is concerned with the influence on Darwin of Hume's Treatise of Human Nature and An Enquiry Concerning Human Understanding and does not even mention Dialogues Concerning Natural Religion!

Daniel Dennett in Darwin's Dangerous Idea: Evolution and the Meanings of Life does describe some connections between Hume's thinking in the Dialogues and Darwin's evolution by natural selection. But in a chapter is entitled "Hume's Close Encounter", Dennett's point is "look how close Hume got to Darwin". Interpreting Hume in the light of Darwin strikes me as a cart-before-horse argument, reminiscent of David Lodge's fictional thesis on the influence of T. S. Eliot on Shakespeare. Instead, we should be looking for Hume's influence on Darwin!

So, is there any evidence that Darwin was familiar with Hume? The answer is yes, in abundance! Darwin kept a list of books to be read and Hume's works feature several times:

• Hume's Essay on Human understanding {(Sometime)}
  
• Hume's Essay
  
• Life of David Hume — (new Edit) by Bell recommended by Erasmus
  
• Hume's life of himself with corres: with Rousseau
• Humes dialogues & Nat. Hist of Religion
  
• Hume Hist. Engl. Vol 5 & 6. 
• 7th & 8th Vol of Hume's England — Admirable
  
• Hume's Essays. 2 Vol.
  
• 2. vols of Hume's History
  
• Hume's Hist of England. to end of the beginning of Elizabeth.
  

Plus Darwin lists Burton's Life of David Hume twice in his list, the second time with the verdict "poor". In fact, although I haven't totted up all of the books Darwin read, it seems likely that Hume is among the most common authors, if not the most common author, in Darwin's list!

So it is clear that Darwin read Hume's Dialogues, but was his later writing influenced by them? Well Dennett is right to point out how close Hume got to some of Darwin's key ideas:

Hume on the Struggle for Existence and War of Nature

"And why should man, added he, pretend to an exemption from the lot of all other animals? The whole earth, believe me, PHILO, is cursed and polluted. A perpetual war is kindled amongst all living creatures. Necessity, hunger, want, stimulate the strong and courageous: Fear, anxiety, terror, agitate the weak and infirm. The first entrance into life gives anguish to the new-born infant and to its wretched parent: Weakness, impotence, distress, attend each stage of that life: and it is at last finished in agony and horror."

"Observe too, says PHILO, the curious artifices of Nature, in order to embitter the life of every living being. The stronger prey upon the weaker, and keep them in perpetual terror and anxiety. The weaker too, in their turn, often prey upon the stronger, and vex and molest them without relaxation. Consider that innumerable race of insects, which either are bred on the body of each animal, or, flying about, infix their stings in him. These insects have others still less than themselves, which torment them. And thus on each hand, before and behind, above and below, every animal is surrounded with enemies, which incessantly seek his misery and destruction. "

And Hume gets close to Natural Selection: 

"And this very consideration too, continued PHILO, which we have stumbled on in the course of the argument, suggests a new hypothesis of cosmogony, that is not absolutely absurd and improbable. Is there a system, an order, an economy of things, by which matter can preserve that perpetual agitation which seems essential to it, and yet maintain a constancy in the forms which it produces? There certainly is such an economy; for this is actually the case with the present world. The continual motion of matter, therefore, in less than infinite transpositions, must produce this economy or order; and by its very nature, that order, when once established, supports itself, for many ages, if not to eternity. But wherever matter is so poised, arranged, and adjusted, as to continue in perpetual motion, and yet preserve a constancy in the forms, its situation must, of necessity, have all the same appearance of art and contrivance which we observe at present. All the parts of each form must have a relation to each other, and to the whole; and the whole itself must have a relation to the other parts of the universe; to the element in which the form subsists; to the materials with which it repairs its waste and decay; and to every other form which is hostile or friendly. A defect in any of these particulars destroys the form; and the matter of which it is composed is again set loose, and is thrown into irregular motions and fermentations, till it unite itself to some other regular form."

"It is in vain, therefore, to insist upon the uses of the parts in animals or vegetables, and their curious adjustment to each other. I would fain know, how an animal could subsist, unless its parts were so adjusted? Do we not find, that it immediately perishes whenever this adjustment ceases, and that its matter corrupting tries some new form?"

And here are a few parallel passages that suggest to me that Darwin might have been influenced by the Dialogues.

The ship and botched trials analogy

Hume in the Dialogues: "But were this world ever so perfect a production, it must still remain uncertain, whether all the excellences of the work can justly be ascribed to the workman. If we survey a ship, what an exalted idea must we form of the ingenuity of the carpenter who framed so complicated, useful, and beautiful a machine? And what surprise must we feel, when we find him a stupid mechanic, who imitated others, and copied an art, which, through a long succession of ages, after multiplied trials, mistakes, corrections, deliberations, and controversies, had been gradually improving? 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."

Darwin in the Origin of Species: "When we no longer look at an organic being as a savage looks at a ship, as at something wholly beyond his comprehension; when we regard every production of nature as one which has had a history; when we contemplate every complex structure and instinct as the summing up of many contrivances, each useful to the possessor, nearly in the same way as when we look at any great mechanical invention as the summing up of the labour, the experience, the reason, and even the blunders of numerous workmen; when we thus view each organic being, how far more interesting, I speak from experience, will the study of natural history become!"

The house/architect analogy

Hume: "If we see a house, CLEANTHES, we conclude, with the greatest certainty, that it had an architect or builder; because this is precisely that species of effect which we have experienced to proceed from that species of cause."

Darwin: "Throughout this chapter and elsewhere I have spoken of selection as the paramount power, yet its action absolutely depends on what we in our ignorance call spontaneous or accidental variability. Let an architect be compelled to build an edifice with uncut stones, fallen from a precipice. The shape of each fragment may be called accidental; yet the shape of each has been determined by the force of gravity, the nature of the rock, and the slope of the precipice,—events and circumstances, all of which depend on natural laws; but there is no relation between these laws and the purpose for which each fragment is used by the builder. In the same manner the variations of each creature are determined by fixed and immutable laws; but these bear no relation to the living structure which is slowly built up through the power of selection, whether this be natural or artificial selection."

The observation that introduced species thrive in new environments, even though they have not originated there.

Hume in the Dialogues: "LUCULLUS was the first that brought cherry-trees from ASIA to EUROPE; though that tree thrives so well in many EUROPEAN climates, that it grows in the woods without any culture. Is it possible, that throughout a whole eternity, no EUROPEAN had ever passed into ASIA, and thought of transplanting so delicious a fruit into his own country? Or if the tree was once transplanted and propagated, how could it ever afterwards perish? Empires may rise and fall, liberty and slavery succeed alternately, ignorance and knowledge give place to each other; but the cherry-tree will still remain in the woods of GREECE, SPAIN, and ITALY, and will never be affected by the revolutions of human society. It is not two thousand years since vines were transplanted into FRANCE, though there is no climate in the world more favourable to them.

It is not three centuries since horses, cows, sheep, swine, dogs, corn, were known in AMERICA. Is it possible, that during the revolutions of a whole eternity, there never arose a COLUMBUS, who might open the communication between EUROPE and that continent?... Nothing less than a total convulsion of the elements will ever destroy all the EUROPEAN animals and vegetables which are now to be found in the Western world."

Darwin in the Origin of Species: "Still more striking is the evidence from our domestic animals of many kinds which have run wild in several parts of the world: if the statements of the rate of increase of slow-breeding cattle and horses in South-America, and latterly in Australia, had not been well authenticated, they would have been quite incredible. So it is with plants: cases could be given of introduced plants which have become common throughout whole islands in a period of less than ten years. Several of the plants now most numerous over the wide plains of La Plata, clothing square leagues of surface almost to the exclusion of all other plants, have been introduced from Europe; and there are plants which now range in India, as I hear from Dr. Falconer, from Cape Comorin to the Himalaya, which have been imported from America since its discovery."

Superiority of the contrivances of nature to those of art

Hume: "Look round the world: contemplate the whole and every part of it: You will find it to be nothing but one great machine, subdivided into an infinite number of lesser machines, which again admit of subdivisions to a degree beyond what human senses and faculties can trace and explain. All these various machines, and even their most minute parts, are adjusted to each other with an accuracy which ravishes into admiration all men who have ever contemplated them. The curious adapting of means to ends, throughout all nature, resembles exactly, though it much exceeds, the productions of human contrivance; of human designs, thought, wisdom, and intelligence. Since, therefore, the effects resemble each other, we are led to infer, by all the rules of analogy, that the causes also resemble; and that the Author of Nature is somewhat similar to the mind of man, though possessed of much larger faculties, proportioned to the grandeur of the work which he has executed."

Darwin in the Origin: "We have seen that man by selection can certainly produce great results, and can adapt organic beings to his own uses, through the accumulation of slight but useful variations, given to him by the hand of Nature. But Natural Selection, as we shall hereafter see, is a power incessantly ready for action, and is as immeasurably superior to man's feeble efforts, as the works of Nature are to those of Art."

On the inability of finite minds to grasp an infinite deity

Hume in the Dialogues: "The question is not concerning the being, but the nature of God. This, I affirm, from the infirmities of human understanding, to be altogether incomprehensible and unknown to us. The essence of that supreme Mind, his attributes, the manner of his existence, the very nature of his duration; these, and every particular which regards so divine a Being, are mysterious to men. Finite, weak, and blind creatures, we ought to humble ourselves in his august presence; and, conscious of our frailties, adore in silence his infinite perfections, which eye hath not seen, ear hath not heard, neither hath it entered into the heart of man to conceive."

Darwin in his Autobiography:"But then arises the doubt—can the mind of man, which has, as I fully believe, been developed from a mind as low as that possessed by the lowest animal, be trusted when it draws such grand conclusions*? May not these be the result of the connection between cause and effect which strikes us as a necessary one, but probably depends merely on inherited experience? Nor must we overlook the probability of the constant inculcation in a belief in God on the minds of children producing so strong and perhaps an inherited effect on their brains not yet fully developed, that it would be as difficult for them to throw off their belief in God, as for a monkey to throw off its instinctive fear and hatred of a snake."

*Note the nice evolutionary twist added by Darwin here!

The balance of happiness/misery and pain/pleasure

Hume: "The only method of supporting Divine benevolence, and it is what I willingly embrace, is to deny absolutely the misery and wickedness of man. Your representations are exaggerated; your melancholy views mostly fictitious; your inferences contrary to fact and experience. Health is more common than sickness; pleasure than pain; happiness than misery. And for one vexation which we meet with, we attain, upon computation, a hundred enjoyments."

Darwin:"if we look to all sentient beings, whether there is more of misery or of happiness;—whether the world as a whole is a good or a bad one. According to my judgment happiness decidedly prevails, though this would be very difficult to prove. If the truth of this conclusion be granted, it harmonises well with the effects which we might expect from natural selection. If all the individuals of any species were habitually to suffer to an extreme degree they would neglect to propagate their kind; but we have no reason to believe that this has ever or at least often occurred. Some other considerations, moreover, lead to the belief that all sentient beings have been formed so as to enjoy, as a general rule, happiness."

Hume: "Admitting your position, replied PHILO, which yet is extremely doubtful, you must at the same time allow, that if pain be less frequent than pleasure, it is infinitely more violent and durable. One hour of it is often able to outweigh a day, a week, a month of our common insipid enjoyments; and how many days, weeks, and months, are passed by several in the most acute torments? Pleasure, scarcely in one instance, is ever able to reach ecstasy and rapture; and in no one instance can it continue for any time at its highest pitch and altitude. The spirits evaporate, the nerves relax, the fabric is disordered, and the enjoyment quickly degenerates into fatigue and uneasiness. But pain often, good God, how often! rises to torture and agony; and the longer it continues, it becomes still more genuine agony and torture. Patience is exhausted, courage languishes, melancholy seizes us, and nothing terminates our misery but the removal of its cause, or another event, which is the sole cure of all evil, but which, from our natural folly, we regard with still greater horror and consternation."

Darwin: "Now an animal may be led to pursue that course of action which is the most beneficial to the species by suffering, such as pain, hunger, thirst, and fear,—or by pleasure, as in eating and drinking and in the propagation of the species, &c. or by both means combined, as in the search for food. But pain or suffering of any kind, if long continued, causes depression and lessens the power of action; yet is well adapted to make a creature guard itself against any great or sudden evil. Pleasurable sensations, on the other hand, may be long continued without any depressing effect; on the contrary they stimulate the whole system to increased action. Hence it has come to pass that most or all sentient beings have been developed in such a manner through natural selection, that pleasurable sensations serve as their habitual guides. We see this in the pleasure from exertion, even occasionally from great exertion of the body or mind,—in the pleasure of our daily meals, and especially in the pleasure derived from sociability and from loving our families. The sum of such pleasures as these, which are habitual or frequently recurrent, give, as I can hardly doubt, to most sentient beings an excess of happiness over misery, although many occasionally suffer much."

Well, what does all this mean? It is uncertain to me whether these parallels reflect a direct influence of Hume's Dialogues on Darwin and if so, if there was a conscious or unconscious decision on Darwin's behalf to exploit them. 

Alternatively, Darwin may have encountered these arguments in a third source that used, or was used by, Hume (e.g. Paley). 

Or the resemblance could be purely coincidental. 

But, in conclusion, it is intriguing to see how far great minds think alike!