Next we must notice that besides our own subjectivities, we have cognizance of being surrounded by many other inferred subjectivities more or less like in kind (i. e. other human minds); and also yet many other inferred subjectivities more or less unlike, but all inferior (i. e. the minds of lower animals, young children, and idiots). Following Clifford, I will call these inferred subjectivities by the name of ejects, and assign to them the symbol _y_. Thus, in the following discussion, _x_ = the objective world, _y_ = the ejective world, and _z_ = subjective world. Now, the theory of Monism supposes that _x_, _y_, and _z_ are all alike in kind, but present no definite teaching as to how far they may differ in degree. We may, however, at once allow that between the psychological value of _z_ and that of _y_ there is a wide difference of degree; and also that, while the value of _z_ is a fixed quantity, that of _y_ varies greatly in the different parts of the area _y_. Our scheme, therefore, will now adopt this form--
But the important question remains how we ought to shade _x_. According to Clifford, this ought scarcely to be shaded at all, while according to theologians (and theists generally) it ought to be shaded so much more deeply than either _y_ or _z_, that the joint representation in one diagram would only be possible by choosing for the shading of _x_ a colour different from that employed for _y_ and _z_, and assigning to that colour a representative value higher than that assigned to the other in the ratio of one to infinity. It will be my object to estimate the relative probability of these rival estimates of the psychological value of _x_.
Starting from _z_ as our centre, we know that this is an isolated system of subjectivity, and hence we infer that all _y_ is composed of analogous systems, resembling one another as to their isolation, and differing only in their degrees of psychological value. Now this, translated into terms of _x_ (or into terms of objectivity) means that _z_ is an isolated system of matter in motion, and that the same has to be said of all the constituent parts of _y_. In other words, both subjectivity and ejectivity are only known under the condition of being isolated from objectivity; which, obversely considered, means that the matter in motion here concerned is temporarily separated off from the rest of the objective world, in such wise that it forms a distinct system of its own. If any part of the objective world rudely forces its way within the machinery of that system, it is at the risk of disarranging the machinery and stopping its work--as is the case when a bullet enters the brain. Such converse as the brain normally holds with the external world, is held through the appointed channels of the senses, whereby appropriate causation is supplied to keep the otherwise isolated system at work. We know, from physiological evidence, that when such external causation is withheld, the isolated system ceases to work; therefore, the isolation, although complete under one point of view, under another point of view is incomplete. It is complete only in the sense in which the isolation of a machine is complete--i. e. it is in itself a working system, yet its working is ultimately dependent upon causation supplied from without in certain appropriate ways. This truth is likewise testified to on the obverse aspect of psychology. For analysis shows that all our mental processes (however complex they may be internally) are ultimately dependent on impressions of the external world gained through the senses. Whether regarded objectively or subjectively, therefore, we find that it is the business of the isolated system to elaborate, by its internal processes, the raw materials which are supplied to it from without. Seeing, then, that the isolation of the system is thus only partial, we may best apply to it the term circumscribed. Such partial isolation or circumscription of matter in motion--so that it shall in itself constitute a little working microcosm--appears to be the first condition to the being of a subjective personality. Why, then, does not the working of a machine present a subjective side?