reply to one of his critics, “I hold to be unworthy of a philosopher and a searcher after truth. I believe I shall do better and more advisedly if I meet so many indications of ill breeding with the light of faithful and conclusive observation.”[15] To many of the attacks made on his discovery or on himself, he therefore did not condescend to reply. And when from the eminence of his opponents he felt called upon to do so, he replied with the utmost courtesy and kindliness. But whilst admitting the high claims to distinction on other grounds of his antagonist, he proceeded on this particular question to utterly demolish him with clear facts and stern irrefutable arguments and experiments. He called upon his opponents to observe the facts and make the experiments for themselves, instead of citing the opinions of authors centuries old, or making long discourses on spirits, fuliginous vapours, and the tides of Euripus. This is well illustrated in his replies to Riolan. The arguments of Riolan would hardly seem to have entitled him to the honour of the special notice of the great discoverer. But probably his position as Anatomist in the University of Paris, and of physician to the Queen-Mother, Marie de Medicis, made Harvey pick out his criticisms as a suitable excuse for replying to his opponents. Harvey’s mode of argument is well shown by the following admirable remarks on the Manner and Order of Acquiring Knowledge, in his introduction to the work on “The Generation of Animals”: “Sensible things are of themselves and antecedent; things of intellect however are consequential and arise from the former, and indeed we can in no way attain to them without the help of the others. And hence it is that without the due admonition of the senses, without frequent observation and reiterated experiment, our mind goes astray after phantoms and appearances. Diligent observation is therefore requisite in every science, and the senses are to be frequently appealed to. We are, I say, to strive after personal experience, not to rely on the experience of others: without which indeed no one can properly become a student of any branch of natural science.” Referring to his own particular work he says: “I would not have you therefore, gentle reader, to take anything on trust from me concerning the Generation of Animals: I appeal to your own eyes as my witness and judge. For as all true science rests upon those principles which have their origin in the operation of the senses, particular care is to be taken that by repeated dissection the grounds of our present subject be fully established.... The method of investigating truth commonly pursued at this time therefore is to be held erroneous and almost foolish, in which so many inquire what others have said, and omit to ask whether the things themselves be actually so or not.” [13] De Generatione Ex. lxviii. [14] Aubrey, _loc. cit._ [15] _Vide_ Second Reply to Riolan, p. 133 post.