ON THE NATUEE OF THE NOTION OF EXTERNALITY. 207 wave theory, and of chemical processes by the atomic theory. The essential difference between the first distinction and this one, may perhaps be sufficiently expressed by saying that this distinguishes between the nature of physical events as they appear to us, and what is thought of as being their true nature ; whereas the former, that with which we are here specially concerned, is drawn between the order in which perceptions make their appearance (or, rather, their want of order), and what is thought of as being the true order of physical events. Having thus cleared the ground, we can now resume our general argument. Let us take one or two examples of the simplest possible kind. We go out for a stroll in the woods, and have our attention attracted by a wild flower. Can we ' account for ' that flower being as it is by an examination of the sensations, thoughts, etc., which were passing through our mind previous to our coming in sight of it ? No, we refer the completed stage of the flower to a connected series of events different from these. We consider it as having sprung up from a seed ; and, if botanically inclined, re- present to ourselves its different stages of growth with all the processes, chemical and physical, on which that growth is dependent. We resume our way, when suddenly we hear the sound of a tree-limb snapping overhead, and step aside just in time to avoid it in its fall. Does that sound follow, as effect on cause, on the mental phenomena which preceded it ? Is the cause even of the bough's fall to be found in the noise which, it is granted, is so far connected with that event as to have served as a warning to us ? Again, no. To ' account for ' the fall, we examine the fallen limb, and find traces of where a large fungus has been eating into the junction between it and the trunk. We conclude that this gradual growth has, by destroying the vitality of the branch and so rendering it unable to support its own weight, brought about the occurrence in which we are interested. But we have never seen that fungus, or been otherwise aware of its presence, until after the event in question ; when we imaginatively re- construct the causes to which that event is due. Thus we cannot explain the occurrence without going outside the mental experiences which preceded it, and, in point of time, led up to our perception of it. These examples have purposely been chosen from changes in inanimate nature. But exactly the same principle ap- plies, so far as the individual consciousness is concerned, to events in which other conscious beings play a part.
