It is well-known that those who have charge of young infants, that it is difficult to feel sure when certain movements about their mouths are really expressive; that is when they really smile. Hence I carefully watched my own infants. One of them at the age of forty-five days, and being in a happy frame of mind, smiled... I observed the same thing on the following day: but on the third day the child was not quite well and there was no trace of a smile, and this renders it probable that the previous smiles were real.

I have rarely read anything which has interested me more, though I have not read as yet more than a quarter of the book proper. From quotations which I had seen, I had a high notion of Aristotle's merits, but I had not the most remote notion what a wonderful man he was. Linnaeus and Cuvier have been my two gods, though in very different ways, but they were mere schoolboys to old Aristotle.

Great is the power of steady misrepresentation; but the history of science shows that fortunately this power does not long endure.

On your life, underestimating the proclivities of finches is likely to lead to great internal hemorrhaging.

I had gradually come, by this time [1839-01], to see that the Old Testament from its manifestly false history of the world, with the Tower of Babel, the rainbow as a sign, etc., etc. and from its attributing to God the feelings of a revengeful tyrant, was no more to be trusted than the sacred books of the Hindoos, or the beliefs of any barbarian.

I must begin with a good body of facts and not from a principle (in which I always suspect some fallacy) and then as much deduction as you please.

Animals manifestly enjoy excitement, and suffer from annul and may exhibit curiosity.