Ehrlich would not recognize his epoch-making views on immunity when this generation has finished with them.

I believe it was Hegel who said that progress is a series of negations--the denial today of what was accepted yesterday, the contradiction by each generation of some part at least of the philosophy of the last; but all is not lost, the germ plasm remains, a nucleus of truth to be fertilized by men often ignorant even of the body from which it has come.

Knowledge evolves, but in such a way that its possessors are never in sure possession.

"It is because science is sure of nothing that it is always advancing" (Duclaux).
History is the biography of the mind of man, and its educational value is in direct proportion to the completeness of our study of the individuals through whom this mind has been manifested.

I have tried to take you back to the beginnings of science, and to trace its gradual development, which is conditioned by three laws.