With respect to the theological view of the question; this is always painful to me.—I am bewildered.—I had no intention to write atheistically. But I own that I cannot see, as plainly as others do, & as I shd. wish to do, evidence of design and beneficence on all sides of us. There seems to me too much misery in the world. I cannot persuade myself that a beneficent & omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of caterpillars, or that a cat should play with mice. Not believing this, I see no necessity in the belief that the eye was expressly designed. On the other hand, I cannot be contented to view this wonderful universe, and especially the nature of man, & to conclude that everything is the result of brute force. I am inclined to look at everything as resulting from designed laws, with the details, whether good or bad, left to the working out of what we may call chance. Not that this notion at all satisfies me. I feel most deeply that the whole subject is too profound for the human intellect. A dog might as well speculate on the mind of Newton.—Let each man hope and believe what he can.

Darwin continues in the same letter:

Certainly I agree with you that my views are not at all necessarily atheistical. The lightning kills a man, whether a good one or a bad one, owing to the excessively complex action of natural laws.—A child (who may turn out an idiot) is born by action of even more complex laws,—and I can see no reason, why a man, or other animal, may not have been aboriginally produced by other laws; & that all these laws may have been expressly designed by an omniscient Creator, who foresaw every future event & consequence. But the more I think the more bewildered I become; as indeed I have probably shown by this letter (CCD 8, 223 [May 22, 1860]).

The question for Darwin came down to whether the notion of an “undesigned nature” made any sense. Two months later, after continuing to ponder, Darwin wrote again to Gray, and again showed that he was still in a quandary:

One more word on “designed laws” & “undesigned results.” I see a bird which I want for food, take my gun and kill it, I do this designedly.—An innocent & good man stands under a tree and is killed by a flash of lightning. Do you believe (& I really shd. like to hear) that God designedly killed this man? Many or most persons do believe this; I can’t and don’t.—If you believe so, do you believe that when a swallow snaps up a gnat that God designed that that particular sparrow shd. snap up that particular gnat at that particular instant? I believe that the man and the gnat are in the same predicament.—If the death of neither man nor gnat are [sic] designed, I see no reason to believe that theirfirst birth or production shd. be necessarily designed. Yet, as I said before, I cannot persuade myself that electricity acts, that the tree grows, that man aspires to the loftiest conceptions all from blind, brute force (CCD vol. 8, 275 [ July 3, 1860]).+

These letters to his close associates must be taken to disclose some of Darwin’s deepest thoughts in 1860–1861 on the subject of divine intelligence in the creation of species. What do the passages tell us? Strictly speaking they tell us three things that are not mutually consistent:

(1) that Darwin had never intended to write “atheistically” (by itself, of course, that does not mean he had no atheistical leanings);

(2) that he can see no evidence of “design” (or, therefore, an omniscient God) in natural productions; and

(3) the whole subject of design and God is too profound for him to know what to believe.

Perhaps God created natural laws at the beginning and then left the world alone so as to allow His laws to play out according to an invisible divine plan. But it is not clear that Darwin really believed that. His ultimate refuge in all the passages reproduced above (and many more) was that the whole question was too profound for him to take it on.