It may be doubted that there are many other animals which have played so important a part in the history of the world as have these lowly organized creatures.

Intelligence is based on how efficient a species became at doing the things they need to survive.

The moral faculties are generally esteemed, and with justice, as of higher value than the intellectual powers. But we should always bear in mind that the activity of the mind in vividly recalling past impressions is one of the fundamental though secondary bases of conscience. This fact affords the strongest argument for educating and stimulating in all possible ways the intellectual faculties of every human being.

I cannot see ... evidence of design and beneficence ... There seems to me too much misery in the world.

After my return to England it appeared to me that by following the example of Lyell in Geology, and by collecting all facts which bore in any way on the variation of animals and plants under domestication and nature, some light might perhaps be thrown on the whole subject.

The formation of different languages and of distinct species and the proofs that both have been developed through a gradual process, are curiously parallel.

Nothing is easier than to admit in words the truth of the universal struggle for life, or more difficult--at least I have found it so--than constantly to bear this conclusion in mind.