"I have no special competence to be able to pass judgment on Kropotkin as a scientist. I know that in his younger days he had rendered remarkable services to geography and to geology; I appreciate the great value of his book Mutual Aid ... It seems, however, to me that he lacked something to make him a real man of science; the capacity to forget his desires and preconceptions in order to observe the facts with an impassive objectivity. He seemed to me to be rather what I should call a poet of science. He might have been able to arrive at new truths by intuitive genius, but others would have had to verify these truths; men with less genius or no genius at all, but better gifted with what is called the scientific spirit. Kropotkin was too passionate to be an exact observer."