unifying and regulatory principle to the _operation_ of an unknown power, a directive _force_, an archæus, an entelechy or a soul?” (_Loc. cit._, p. 285—italics mine.) The objection, however, does not apply to these terms used in their Aristotelian sense. In the philosophy of the Stagirite, the soul, like all other entelechies, is a cause in the _entitive_, but not in the _dynamic_, order of things. Its efficacy is _formal_, not _efficient_. It is not an agent, but a specifying type. The organism must be integrated, specified, and existent _before_ it can operate, and hence its integration and specification by the soul is prior to all vital activity. The soul is a constituent of being and not an immediate principle of action. The soul is not even an entity (in the sense of a complete and separate being), but rather an incomplete entity or constituent of an entity. It takes a complete entity to be an agent, and the soul or vital entelechy is not an independent existent, which is somehow inserted into the organism, but an incomplete being which has no existence of its own, but only coexistence, in the composite that it forms with the organism. Nor is there any such thing as a special vital force resident in the organism. The executive factors in all vital operations of the organic order are the physicochemical energies, which are native to matter in general. These forces, as we have seen, receive a reflexive orientation and are elevated to a higher plane of efficiency by reason of their association with an entelechy superior to the binding and type-determining principles present in inorganic units, but they are not supplanted or superseded by a new executive force. Wilson’s fear, therefore, that the experimental analysis of life is discouraged by vitalism, inasmuch as this conception _subtracts something from the efficiency of the physicochemical forces_, is groundless in the case of hylomorphic vitalism, but is well-founded in the case of such systems as the neo-vitalism of Driesch and the spiritualism of Descartes.