Fear is the parent of cruelty.

Where nature is sovereign, there is no need of austerity and self-denial.

There is always a part of our being into which those who are dearer to us far than our own lives are yet unable to enter.

Science rests on reason and experiment, and can meet an opponent with calmness; [but] a creed is always sensitive.

Carelessness is inexcusable, and merits the inevitable sequence.

What is called virtue in the common sense of the word has nothing to do with this or that man's prosperity, or even happiness.

Philosophy goes no further than probabilities, and in every assertion keeps a doubt in reserve.