Page:Mind (New Series) Volume 15.djvu/68

 54 HENRY RUTGERS MARSHALL : conscious states and the activities of our complex nervous system ; and I shall ask the reader to consider for a moment the evidence derived from this source. It is perhaps possible for the physicist, who assumes the indestructibility of physical atoms, to hold that a given atom, or a given molecule formed of atoms, may in two different moments be one and the same in all respects and under all conditions, although it is to be noted that he is unable to prove his assertion empirically, and is somewhat hesitant nowadays in his defence of the validity of this conception. But when we consider such inorganic masses as we are able to study with care we note that as the constitution of these masses becomes more and more complex, the return to their original condition after a reaction of any kind becomes more and more unlikely ; for the reason that the primary reaction then involves a readjustment of many relations ; and in consequence a return to the original condition involves a physical impulse, or series of impulses, which shall restore all of these many relations at the same moment. Thus the evaporation of water from a body of sand leaves it dry, and free to be blown by the wind out of its original position ; and the shifting sand may divert the course of some little stream- let, which in its turn may cause many changes in the sur- face of the ground. To replace all of these changed parts of the comparatively simple inorganic masses which are here considered would evidently be impossible without a very complex set of influences which are not likely to occur coincidently. It thus appears that, even with inorganic matter of a rela- tive simplicity of constitution, it is very difficult for us to conceive of exact recurrences of form and conditions in any two successive moments : and in the fact that we look for different reactions in the two moments we really tacitly assume that each bit of inorganic matter which can be observed is necessarily a different bit of matter, and not the same, before and after it has received, and has reacted to, an impulse of any kind which it has received from its environment. When we turn to the consideration of living matter we find the conditions of complication immensely increased. The very simplest bit of living matter is very complex in relation to any inorganic matter such as we have considered in our previous illustrations : and the nervous system of man in which the psychologist takes a special interest is a special kind of living matter of an extraordinarily complex nature, and with its parts bound together in a system of immensely complex minor systems.