To many people virtue consists chiefly in repenting faults, not in avoiding them.

Be attentive, feel nothing in vain, measure and compare: this is the whole law of philosophy.

The more experiences and experiments accumulate in the exploration of nature, the more precarious the theories become. But it is not always good to discard them immediately on this account. For every hypothesis which once was sound was useful for thinking of previous phenomena in the proper interrelations and for keeping them in context. We ought to set down contradictory experiences separately, until enough have accumulated to make building a new structure worthwhile.

Deliberate virtue is never worth much: The virtue of feeling or habit is the thing.

To make astute people believe one is what one is not is, in most cases, harder than actually to become what one wishes to appear.

Whenever he composes a critical review, I have been told, he gets an enormous erection.

With God thoughts are colors, with us they are pigments-even the most abstract one may be accompanied by physical pain.