For it is by no means the case that the mechanical theory, with its premisses and principles, is the interpretation that best fits the facts, and that most naturally arises out of a calm consideration of the animate world. It is an artificial scheme, and astonishing energy has been expended on the attempt to fit it to the actual world, that it may make this orderly and translucent. It certainly yields this service so far, but not without often becoming a kind of strait-jacket, and revealing itself as an artificiality. In so far as the special problems of biology are concerned, we shall afterwards follow our previous method of taking our orientation from those specialists in the subject who, in reaction from the one-sidedness of the mechanical doctrine, have founded the “neo-vitalism” of to-day. Here we are only concerned with the generalities and presuppositions of the theory. We must dispute even the main justification of the theory, which is sought for in the old maxim of parsimony in the use of principles of explanation (_entia_, and also _principia, præter necessitatem non esse multiplicanda_), and in Kant’s “regulative principle,” that science must proceed as if everything could ultimately be explained in terms of mechanism. For surely our task is to try to explain things, not at any cost with the fewest possible principles, but rather with the aid of those principles which appear most correct. If nature is not fundamentally simple, then it is not scientific but unscientific to simplify it theoretically. And the proposition bracketed above has its obvious converse side, that while entities and principles must not be multiplied except when it is necessary, on the other hand their number must not be arbitrarily lessened. To proceed according to the fundamental maxims of the mechanistic view can only be wholesome for a time and, so to speak, for pædagogical reasons. To apply them seriously and permanently would be highly injurious, for, by prejudging what is discoverable in nature, it would tend to prevent the calm, objective study of things which asks for nothing more than to see them as they are. It would thus destroy the fineness of our appreciation of what there really is in nature. This is true alike of forcible attempts to reduce the processes of life to mechanical processes, and of the Darwinian doctrine of the universal dominance of utility. Both bear unmistakably the stamp of foregone conclusions, and betray a desire for the simplest, rather than for the most correct principles of interpretation.