The sure conviction that we could if we wanted to is the reason so many good minds are idle.

As I take up my pen I feel myself so full, so equal to my subject, and see my book so clearly before me in embryo, I would almost like to try to say it all in a single word.

Those who never have time do least

What you have been obliged to discover by yourself leaves a path in your mind which you can use again when the need arises.

We often have need of a profound philosophy to restore to our feelings their original state of innocence, to find our way out of the rubble of things alien to us, to begin to feel for ourselves and to speak ourselves, and I might almost say to exist ourselves.

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.

Just as the performance of the vilest and most wicked deeds requires spirit and talent, so even the greatest demand a certain insensitivity which under other circumstances we would call stupidity.