(3) One more point may receive passing notice. It is clear that if physical nature is really a society or a number of societies[125] of experiencing subjects, we must admit that, from the special character of our human experience with its peculiar interests and purposes, we are normally debarred from social communion with any members of the system except those who are most akin in their special type of purposive life to ourselves. Of the vast majority of the constituents of the physical order it must always be true that, while we may be convinced, on grounds of general metaphysical theory, that they possess the character we have ascribed to them, we have no means of verifying this conclusion in specific cases by the actual direct recognition of the individual life to which they belong, and consequent establishment of actual social relations with them. Yet it does not follow that we are always absolutely debarred from such direct social relations with extra-human sentient life. The “threshold of intercommunicability” between physical nature and human intelligence may conceivably be liable to fluctuations under conditions at present almost entirely unknown. Conceivably the type of experience represented in literature by the great poets to whom the sentient purposive character of physical nature has appealed with the force of a direct revelation of truth, and known in some degree to most men in certain moods, may depend upon a psychological lowering of this threshold. It is thus at least a possibility that the poet’s “communion with nature” may be more than a metaphor, and may represent some degree of a social relation as real as our more normal relations with our human fellows and the higher animals. It may be true that in the relations of man with nature, as in his relations with man, it is the identity of purpose and interest we call love which is the great remover of barriers.