LIMITING FACTORS IN THE HISTORY OF SCIENCE 



audacity in Kenelm Digby,^ whose discussions of the development 

 of the chick are remarkable for their naturalistic tone, for their con- 

 viction that the processes of development are not beyond the reach 

 of the reason and imagination of man. It is ironic that Digby, who did 

 little or nothing himself to advance our knowledge, should have 

 spoken thus, and that his great contemporary, William Harvey, to 

 whom we are indebted for so many advances in embryology, was led 

 to despair of understanding development Another interesting point 

 that emerges from the same period is that such mental audacity can 

 go, perhaps, too far, as when Descartes^ and Gassendi^ built up an 

 embryology more geometrico demonstrata, in which the facts were 

 relegated to an inferior position and the theory was all. 



But not only must the right concepts be chosen, the wrong ones 

 must be abandoned. One of the principal necessities which has faced 

 investigators since the earliest times has been the recognition of silly 

 questions in order to leave time for the examination of serious ones. 

 It was presumably inevitable that the pseudo-problems concerning 

 the entry of the soul into the embryo should be taken seriously until 

 a very late date. But a more typical instance of a meaningless question 

 may be found in the dispute about what parts of the egg form the 

 chick and which feed it. The tacit assumption here was that since to 

 common sense food and flesh are different things, there must be in 

 the hen's egg, aside from a sufficient provision of food, some sort of 

 pre-flesh out of which the embryo can be made. Not until 165 1 did 

 this pseudo-problem go out of currency in the light of Harvey's 

 demonstration of the unsoundness of the assumption. 



The expulsion of ethics from biology and embryology forms 

 another excellent example. That good and bad, noble and ignoble, 

 beautiful and ugly, honourable and dishonourable, are not terms 

 with a biological meaning is a proposition which it has taken many 

 centuries for biologists to realise. 



Ideas of good and bad entered biology partly under the concept 

 of "perfection." In 1260 Albertus was maintaining that male chicks 

 always hatched from the more spherical eggs and female chicks 

 from the more oval eggs, because the sphere is the most perfect of 

 all figures in solid geometry, and the male the more perfect of the 



^ Two Treatises, in the one of which the Nature of Bodies, in the other the Nature of 

 Man's Soule, is looked into, in way of discovery of the Immortality of Reasonable 

 Soules, 1644. 



^ L' Homme, et la formation du Foetus, etc., 1664. ^ Opera, 1658. 



