It is a duty to call particular attention to the recent work of M. Janet, 'Les Causes Finales.' Although M. Janet concedes, perhaps, too much to the opponents of finality, his treatise contains the ablest and most adequate discussion of the various problems suggested by the indications which organic nature gives of design that has yet appeared. It is eminently worthy of a careful study. I am glad to know that a translation of this valuable work is in progress.
Among the masters of biological science, Cuvier, V. Baer, Agassiz, and R. Owen may be named, as among those who have set the highest value on the principle of finality. The essay on Classification of Agassiz, and the various essays which Von Baer has published at different times, on what he calls "Zielstrebigkeit," are specially important.
"The _savants_ are generally too much disposed to confound the doctrine of final cause with the hypothesis of an invisible force acting without physical means, as a _deus ex machinâ_. These two hypotheses, far from reducing themselves the one to the other, are in explicit contradiction; for he who says _design_ says at the same time _means_, and, consequently, causes adapted to produce a certain effect. To discover this cause is by no means to destroy the idea of design; it is, on the contrary, to bring to light the condition, _sine quâ non_, of the production of the end. To make clear this distinction we cite a beautiful example, borrowed from M. Claude Bernard. How does it happen, says this eminent physiologist, that the gastric juice, which dissolves all aliments, does not dissolve the stomach itself, which is of precisely the same nature as the aliments with which it is nourished? For a long time the vital force was supposed to intervene--that is to say, an invisible cause which, in some way, suspended the properties of the natural agents, to prevent their producing their necessary effects. The vital force would, by a sort of moral _veto_, forbid the gastric juice to touch the stomach. We see that this would be a real miracle. Everything is explained when we know that the stomach is lined with a coating or varnish which is not attacked by the gastric juice, and which protects the walls which it covers. Who does not see that in refuting the omnipotence of the vital force, very far from having weakened the principle of finality, we have given to it a wonderful support? What could the most perfect art have done to protect the walls of the stomach, but invent a precaution similar to that which exists in reality? And how surprising it is that an organ destined to secrete and use an agent most destructive to itself, is found armed with a protective tunic, which must have always coexisted with it, since otherwise it would have been destroyed before having had time to procure for itself this defence--which excludes the hypothesis of long gropings and happy occurrences."--Janet, 'Final Causes and Contemporaneous Physiology,' Presb. Quart. Rev., April 1876.