An autocratic system of coercion, in my opinion, soon degenerates. For force always attracts men of low morality, and I believe it to be an invariable rule that tyrants of genius are succeeded by scoundrels. For this reason I have always been passionately opposed to systems such as we see in Italy and Russia to-day.

My only refuge, as a serious young man, from the despair of my financial burden to my family, is that I did everything I could to never permit myself any amusements or diversions except those afforded by my studies.

The consequence was a positively fanatic [orgy of] freethinking coupled with the impression that youth is being deceived by the state through lies; it was a crushing impression

To sense that behind anything that can be experienced there is a something that our mind cannot grasp and whose beauty and sublimity reaches us only indirectly and as a feeble reflection, this is religiousness. In this sense I am religious.

I have never obtained any ethical values from my scientific work.

To obtain an assured favorable response from people, it is better to offer them something for their stomachs instead of their brains.

The future is not a gift-it is an achievement.