Man in his arrogance thinks himself a great work.

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?

The great variability of all the external differences between the races of man, likewise indicates that they cannot be of much importance; for if important, they would long ago have been either fixed and preserved, or eliminated.

On the ordinary view of each species having been independently created, we gain no scientific explanation.

I believe there exists, & I feel within me, an instinct for the truth, or knowledge or discovery, of something of the same nature as the instinct of virtue, & that our having such an instinct is reason enough for scientific researches without any practical results ever ensuing from them.

Every serious scientific worker is painfully conscious ... of being relegated to an ever-narrowing sphere of knowledge.