If any philosopher had been asked for a definition of infinity, he might have produced some unintelligible rigmarole, but he would certainly not have been able to give a definition that had any meaning at all.

Hitler is an outcome of Rousseau.

Ideas and principles that do harm are as a rule, though not always, cloaks for evil passions.

Neither acquiescence in skepticism nor acquiescence in dogma is what education should produce.

They must often change, who would be constant in happiness or wisdom. Those who continually search for happiness will never find it. Happiness is made, not found. To be without some of the things you want is an indispensable part of happiness.

Collective wisdom, alas, is no adequate substitute for the intelligence of individuals. Individuals who opposed received opinions have been the source of all progress, both moral and intellectual. They have been unpopular, as was natural.

In all affairs it's a healthy thing now and then to hang a question mark on the things you have long taken for granted.