principle or presumption of science which must be adhered to at any cost, namely:
that throughout organic nature, amid all changes of individual creatures, the species maintain themselves unaltered (die Species derselben sich unverändert erhalten)—according to the formula of the schools, quaelibet natura est conservatrix sui. Now it is clear that if some magical power of the imagination, or the artifice of men, were capable of modifying in the bodies of animals the reproductive faculty itself, of transforming Nature's original model or of making additions to it, which changes should then become permanent in subsequent generations, we should no longer know from what original Nature had begun, nor how far the alteration of that original may proceed, nor—since man's imagination knows no bounds—into what grotesqueries of form species might eventually be transmogrified (in welche Fratzengestalt die Gattungen und Arten zuletzt noch verwildern dürften). In view of this consideration, I for my part adopt it as a fundamental principle to recognize no power in the imagination to meddle with the reproductive work of Nature, and no possibility that men, through external, artificial modifications, should effect changes in the ancient original of a species in any such way as to implant those changes in the reproductive process and make them hereditary. For if I admit a single instance of this sort, it is as if I admitted the truth of a single ghost-story or tale of magic. The boundaries of reason are then once for all broken through, and errors rush in by thousands through that opening. There is, meanwhile, no danger that, in adopting this conclusion, I may take a position of blind or stubborn incredulity towards real facts of experience. For all these romantic (abenteuerlich) occurrences have without exception one peculiarity, namely, that they can not be subjected to experiment, but are supposed to be proved merely by casual observations. But whatever, though capable, indeed, of experimental testing, offers no experimental evidence, or employs all sorts of excuses to avoid such a test, is mere fiction and illusion.[1]"
Nothing could better exhibit Kant's characteristic state of mind on biological questions than this passage. There are occasional bits of sound sense in it and of discriminating judgment about scientific method; and there is a certain power of at least seeing where the significant problems lie. Yet, though he had come under the influence of evolutionistic conceptions, and is in these very writings endeavoring to apply genetic methods to certain biological inquiries, he recoils in horror before the idea of admitting that real species are capable of
- ↑ The "Physical Geography" is equally emphatic in repudiating both inheritance of acquired characters and mutation of species: "External things may, indeed, provide the occasions, but they can not be the efficient causes, of the appearance of characters that are necessarily transmitted and inherited. As little as chance or physico-mechanical causes can bring an organic body into existence, just so little can they imprint anything upon the reproductive faculty, that is, produce any effect that is itself reproduced, either as a special form or as a relation of the parts. Air, light and nutrition can modify the growth of an animal body, but they can not furnish this change with a power of reproducing itself after its original causes are no longer operative. . . . For it is not possible that anything should so penetrate into the reproductive faculty as to be capable of gradually removing the creature from its original determination and bringing about a real and self-perpetuating departure from the specific type (Ausartung).
