I am a firm believer, that without speculation there is no good and original observation.

It is like confessing to a murder.

I can indeed hardly see how anyone ought to wish Christianity to be true for if so the plain language of the text seems to show that the men who do not believe, and this would include my father, brother and almost all of my friends, will be everlastingly punished. And this is a damnable doctrine.

It is a fatal fault to reason whilst observing, though so necessary beforehand and so useful afterwards.

On seeing the marsupials in Australia for the first time and comparing them to placental mammals: “An unbeliever . . . might exclaim 'Surely two distinct Creators must have been at work'”

If worms have the power of acquiring some notion, however rude, of the shape of an object and over their burrows, as seems the case, they deserve to be called intelligent; for they act in nearly the same manner as would man under similar circumstances.

Sympathy for the lowest animals is one of the noblest virtues with which man is endowed.