For real wealth is the developed productive power of all individuals. The measure of wealth is then not any longer, in any way, labour time, but rather disposable time.

There is no royal road to science, and only those who do not dread the fatiguing climb of its steep paths have a chance of gaining its luminous summits.

Philosophy and the study of the actual world have the same relation to one another as masturbation and sexual love.

Scientific truth is always paradox, if judged by everyday experience, which catches only the delusive appearance of things.

Darwin has interested us in the history of nature's technology.