Thus the separate worlds, in which we are all shut up, must be considered as corresponding so far as they are objective, that is, so far as they approach what we are ultimately obliged to think. I say “corresponding,” because that is the term which expresses the relation between systems which represent the same thing by the same rules, but with different starting-points. Drawings in perspective of the same building from different points of view are such corresponding systems; the parts represented answer each to each, but the same part is near or large in one drawing, and distant and small in another; not, however, by chance, but as a definite consequence of the same laws. Our separate worlds may be compared to such drawings: the things in them are identified by their relations and functions, so that we can understand each other, _i.e._ make identical references, though my drawing be taken from the east, and yours from the west. The things do not look quite the same in our different worlds; besides being taken from different standpoints, both drawings are imperfect and incorrect. But so {19} long as we can make out the correspondence, we have a basis for co-operation and for discussion. Logic shows us the principles and processes by which, under the given influences, these drawings are constructed. _Subjective Idealism_ 8. If we merely hold to the doctrine of separate worlds, without insisting upon their correspondence with each other and with reality, we fall back into the position of subjective idealism, which is a natural completion of common-sense theory, when, instead of turning round to retrace its path, it runs deeper into the _cul-de-sac_. It is a very obvious reflection, that each of us is shut up within his own mind, and much easier to grasp than the reason for assuming a real system which appears differently, though correspondingly, in the centres of consciousness which are ourselves. We cannot get at anything but in terms of consciousness; how can we justify the assumption that our consciousness of a world of objects is rooted in reality, _e.g._, that objects may rightly be treated as persisting and inter-acting when our personal consciousness is withdrawn? And if we once doubt this, then why should we assume that our ideas need be or tend to be consistent with themselves and each other, as for the time they apparently are?