“Lastly, with reference to Lord Kelvin’s statement that ‘modern biologists are coming once more to a firm acceptance of something--and that is “a vital principle.”’ I will not venture to doubt that Lord Kelvin has such persons among his acquaintance. On the other hand, I feel some confidence in stating that a more extensive acquaintance with modern biologists would have led Lord Kelvin to perceive that those whom he cites are but a trifling percentage of the whole. I do not myself know of any one of admitted leadership among modern biologists who is showing signs of ‘coming to a belief in the existence of a vital principle.’ “Biologists were, not many years ago, so terribly hampered by these hypothetical entities--‘vitality,’ ‘vital spirits,’ ‘anima animans,’ ‘archetypes,’ ‘vis medicatrix,’ ‘providential artifice,’ and others which I cannot now enumerate--that they are very shy of setting any of them up again. Physicists, on the other hand, seem to have got on very well with their problematic entities, their ‘atoms’ and ‘ether,’ and ‘the sorting demon of Maxwell.’ Hence, perhaps, Lord Kelvin offers to us, with a light heart, the hypothesis of a ‘a vital principle’ to smooth over some of our admitted difficulties. On the other hand, we biologists, knowing the paralysing influence of such hypotheses in the past, are as unwilling to have anything to do with ‘a vital principle,’ even though Lord Kelvin erroneously thinks we are coming to it, as we are to accept other strange ‘entities’ pressed upon us by other physicists of a modern and singularly adventurous type. Modern biologists (I am glad to be able to affirm) do not accept the hypothesis of ‘telepathy’ advocated by Sir Oliver Lodge, nor that of the intrusions of disembodied spirits pressed upon them by others of the same school. “We biologists take no stock in these mysterious entities. We think it a more helpful method to be patient and to seek by observation of, and experiment with, the phenomena of growth and development to trace the evolution of life and of living things without the facile and sterile hypothesis of ‘a vital principle.’ Similarly, we seek by the study of cerebral disease to trace the genesis of the phenomena which are supposed by some physicists who have strayed into biological fields to justify them in announcing the ‘discovery’ of ‘telepathy’ and a belief in ghosts.” CHAPTER II _THE ADVANCE OF SCIENCE, 1881-1906_