[2] “Averrhoës who made the great Commentary” (Dante). It was Averrhoës (Ebn Roshd) who, in the 12th century, introduced Aristotle to the Mohammedan world, and the “Commentary” referred to was on Aristotle.
[3] What appear to me to be certain resemblances between the Galenical and the modern vitalistic views of Henri Bergson may perhaps be alluded to here. Galen’s vital principle, ἡ τεχνικὴ φύσις (“creative growth”), presents analogies with l’Evolution créatrice: both manifest their activity in producing qualitative change (ἀλλοίωσις, changement): in both, the creative change cannot be analysed into a series of static states, but is one and continuous. In Galen, however, it comes to an end with the development of the individual, whereas in Bergson it continues indefinitely as the evolution of life. The three aspects of organic life may be tabulated thus:—
| δύναμις | ἐνέργεια | ἔργον |
| Work to be done. | Work being done. | Work done, finished. |
| Future aspect. | Present aspect. | Past aspect. |
| Function. | Structure. | |
| The élan vital. | A “thing.” | |
| A changing which cannot be understood as a sum of static parts; a constant becoming, never stopping—at least till the ἔργον is reached. | ||
| Bergson’s “teleological” aspect. | Bergson’s “philosophical” aspect. | Bergson’s “outlook of physical science.” |
Galen recognized “creativeness” (τέχνη) in the development of the individual and its parts (ontogeny) and in the maintenance of these, but he failed to appreciate the creative evolution of species (phylogeny), which is, of course, part of the same process. To the teleologist the possibilities (δυνάμεις) of the Physis are limited, to Bergson they are unlimited. Galen and Bergson agree in attaching most practical importance to the middle category—that of Function.
While it must be conceded that Galen, following Aristotle, had never seriously questioned the fixity of species, the following quotation from his work On Habits (chap. ii.) will show that he must have at least had occasional glimmerings of our modern point of view on the matter. Referring to assimilation, he says: “Just as everything we eat or drink becomes altered in quality, so of course also does the altering factor itself become altered.... A clear proof of the assimilation of things which are being nourished to that which is nourishing them is the change which occurs in plants and seeds; this often goes so far that what is highly noxious in one soil becomes, when transplanted into another soil, not merely harmless, but actually useful. This has been largely put to the test by those who compose memoirs on farming and on plants, as also by zoological authors who have written on the changes which occur according to the countries in which animals live. Since, therefore, not only is the nourishment altered by the creature nourished, but the latter itself also undergoes some slight alteration, this slight alteration must necessarily become considerable in the course of time, and thus properties resulting from prolonged habit must come to be on a par with natural properties.”
Galen fails to see the possibility that the “natural” properties themselves originated in this way, as activities which gradually became habitual—that is to say, that the effects of nurture may become a “second nature,” and so eventually nature itself.
The whole passage, however, may be commended to modern biologists—particularly, might one say, to those bacteriologists who have not yet realised how extraordinarily relative is the term “specificity” when applied to the subject-matter of their science.
[4] In terms of filtration, diffusion, and osmosis.