Charles Darwin

Although much remains obscure, and will long remain obscure, … I am convinced that Natural Selection has been the main but not exclusive means of modification.

It will be seen that I look at the term species, as one arbitrarily given for the sake of convenience to a set of individuals closely resembling each other, and that it does not essentially differ from the term variety, which is given to less distinct and more fluctuating forms. The term variety, again, in comparison with mere individual differences, is also applied arbitrarily, and for mere convenience sake.

The expression often used by Mr. Herbert Spencer of the Survival of the Fittest is more accurate, and is sometimes equally convenient.

It is a curious little world within itself

It is easy to specify the individual objects of admiration in these grand scenes; but it is not possible to give an adequate idea of the higher feelings of wonder, astonishment, and devotion, which fill and elevate the mind.

We will now discuss in a little more detail the struggle for existence.

And thus, the forms of life throughout the universe become divided into groups subordinate to groups.

I should premise that I use the term Struggle for Existence in a large and metaphorical sense, including dependence of one being on another, and including (which is more important) not only the life of the individual, but success in leaving progeny.

If the misery of our poor be caused not by the laws of nature, but by our institutions, great is our sin.

A republic cannot succeed, till it contains a certain body of men imbued with the principles of justice and honour.