§ 4. We may now apply the results obtained in the previous section to the general question as to the “independent” existence of the physical order. In doing so we observe two consequences of the highest importance. (1) Now that we have found that at least a part of that order, namely, the bodies of our fellow-men, are not mere complexes of presentations in our own experience, but have a further existence as themselves experiencing subjects, and are so far “independent” of their actual presentation in our own experience, we can no longer conclude, from the dependence of the physical order for its sensible properties upon presentation to ourselves, that it has no further existence of its own. If one part of that order, which as presented stands on the same footing with the rest, and is, like it, dependent on presentation for its sensible properties, is certainly known to be more than a mere presentation-complex, the same _may_ at least be true of other parts. We can no longer assert of any part of the physical order, without special proof, that its _esse_ is merely _percipi_. We may go a step further. Not only _may_ other parts of the physical order possess a reality beyond the mere fact of being presented to our sense-perception, but they _must_. For (_a_) we have to take note, for the obtaining of our own practical ends, of the factors in our _material_ environment precisely as we have to take note of the purposive behaviour not our own which forms our _social_ environment. Just as our own inner life has no coherent significance except as part of a wider whole of purposive human life, so human society as a system of significant conduct directed to the attainment of ends, cannot be understood without reference to its non-human surroundings and conditions. To understand my own experience, reference must be made to the aims, ideals, beliefs, etc. of the social whole in which I am a member; and to understand these, reference has again to be made to geographical, climatic, economical, and other conditions. Thus of the physical order at large, no less than of that special part of it which consists of the bodies of my fellows, it is true to say that its existence means a great deal more than the fact of its presentation. Unperceived physical existence must be real if I am myself real, because my own inner life is unintelligible without reference to it. (_b_) This conclusion is further strengthened by the evidence supplied by the various sciences, that human life forms part of a great system characterised by evolution or development. If one part of a connected historical development is more than a complex of presentations, the other stages of that development cannot possibly be mere presentation-complexes. Against any “Idealism” which is mere Subjectivism or Presentationism calling itself by a less suspicious name, it would be a sound and fair argument to contend that it reduces evolution to a dream, and must therefore be false.[123]