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'”

I fully subscribe to the judgement of those writers who maintain that of all the differences between man and the lower animal, the moral sense of conscience is by far the most important....It is the most noble of all the attributes of man.

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

I find in the domestic duck that the bones of the wing weigh less and the bones of the leg more, in proportion to the whole skeleton, than do the same bones in the wild duck; and this change may be safely attributed to the domestic duck flying much less, and walking more, than its wild parents.

Attention, if sudden and close, graduates into surprise; and this into astonishment; and this into stupefied amazement.

we are always slow in admitting any great change of which we do not see the intermediate steps

The most important factor in survival is neither intelligence nor strength but adaptability.