rogation of nature, how much matter can do without spiritual help. Let each investigator pursue the method of research which most suits the bent of his genius, and here, as in other departments of science, let each system be judged by its fruits, which cannot fail in the end to be the best sponsors and sureties for its truth. But the physiological inquirer into mind may, if he care to do so, justly protest against the easy confidence with which some metaphysical psychologists disdain physiological inquiry, and ignore its results, without ever having been at the pains to make themselves acquainted with what these results are, and with the steps by which they have been reached. Let theory be what it may, there can be no just question of the duty of observing faithfully all the instances which mental phenomena offer for inductive inquiry, and of striving to realize the entirely new aspect which an exact study of the physiology of the nervous system gives to many problems of mental science. One reflection cannot fail to occur forcibly to those who have pursued this study, namely, that it would have been well could the physiological inquirer, after rising step by step from the investigation of life in its lowest forms to that of its highest and most complex manifestations, have entered upon his investigations of mind without being hampered by any philosophical theories concerning it. The very terms of metaphysical psychology have, instead of helping, oppressed and hindered him to an extent which it is impossible to measure: they have been hobgoblins to frighten him from entering on his path of inquiry, phantoms to lead him astray at every turn after he has entered upon it, deceivers lurking to betray him under the guise of seeming friends tendering help. Let him take all the pains in the world, he cannot express adequately and exactly what he would-neither more nor less-for he must use words which have already meanings of a metaphysical kind attached to them, and which, when used, are therefore for him more or less a misinterpretation. He is thus forced into an apparent encroachment on questions which he does not in the least degree wish to meddle with, and provokes an antagonism without ever designing it; and so one cannot but think it would have been well if he could have had his own words exactly fitting his facts, and free from the vagueness and ambiguity of a former metaphysical use. The article on the "Theory of Vitality," which appeared in 1863, is now reprinted, with a few, mainly verbal, alterations. The aspect of some of the questions discussed in it has been somewhat changed by the progress of inquiry and thought since that time, but it appears to the Author that, great as discussion has been, there are yet considerations respecting vitality that have not been duly weighed. Whether living matter was formed originally, or is now being formed, from non-living matter, by the operation of physical causes and natural laws, are questions which, notwithstanding the lively and vigorous handling which they have had, are far from being settled. Exact experiment can alone put an end to this dispute the one conclusive experiment, indeed, in proof of the origin of living from dead matter, will be to make life. Meanwhile, as the subject is still in the region of discussion, it is permissible to set forth the reflections which the facts seem to warrant, and to endeavour to indicate the direction of scientific development which seems to be foretokened by, or to exist potentially in, the knowledge which we have thus far acquired. This much may be said: that those who oppose the doctrine of so-called spontaneous generation, not on the ground of the absence of conclusive evidence of its occurrence, which they might justly do, but on the ground of what they consider special characteristics of living matter, would do well to look with more insight into the phenomena of non-living nature, and to consider more deeply what they see, in order to discover whether the characteristic properties of life are quite so special and exclusive as they imagine them to be. Having done that, they might go on to consider whether, even if their premisses were granted, any conclusion regarding the mode of origin of life would legitimately follow; whether in fact it would not be entirely gratuitous and unwarrantable to conclude thence the impossibility of the origin of living matter from non-living matter. The etymological import of the words physics and physiology is notably the same; and it may be that, as has been suggested, in the difference of their application lies a hidden irony at the assumption on which the division is grounded. 9, HANOVER Square, W. November 5, 1870. |