IN the issue of NATURE for Feb. 7, p. 200, Mr. Malcolm E. MacGregor revives a form of vitalism that has lain dormant for a number of years ; and well might it have been permitted to do so for as many more. It is surely well recognised that science is only a conceptual scheme which presumably bears some relation to the percepts that it attempts to correlate. What lies outside that scheme may indeed be of the greatest importance, but it is not science. Mr. MacGregor adduces no evidence that the force primarily operating the living cell is an external one. His wishes would be equally fulfilled by some form of hylozoism, but then it would be very difficult to acclaim the view as likely to be a guiding star for biological advance. If one wishes to hold such vitalistic theories as being true, one cannot remain immune from scientific attack except by rigid adherence to some form of dualism, such as that of the great Nicholas of Cusa. Thus, if it be contended, as he did, that there is an external form of experience subject to natural law but separate from an inner form that has no relation to such law and is beyond reason, then no scientific criticism is possible.