Eternal vigilance is the price of knowledge.
One's friends are that part of the human race with which one can be human.
Man's most serious activity is play.
Animals are born and bred in litters. Solitude grows blessed and peaceful only in old age.
Nature is like a beautiful woman that may be as delightfully and as truly known at a certain distance as upon a closer view; as to knowing her through and through; that is nonsense in both cases, and might not reward our pains.
The human mind is not rich enough to drive many horses abreast and wants one general scheme, under which it strives to bring everything.