(_c_) Every element of the physical order fills a position in _space_ and in _time_. Hence any metaphysical problems about the nature of space and time are bound to affect our view of the nature of the physical order. Here, again, there is a point of at least possible contrast between the physical and the psychical. As the accumulation of experience makes it increasingly clearer that the bodies of my fellow-men and my own body, in so far as it is an object perceived like others by the organs of the special senses, exhibit in many respects the same conformity to certain general laws, and are composed of the same constituent parts as the rest of the sensible world, such animated bodies of purposive agents have to be included along with the rest of sensible existence in the physical order. The individual’s purposive individuality has now to be thought of as residing in a distinct factor in his composition of a kind foreign to the physical order, and therefore imperceptible by the senses, _i.e._ as a _mind_ or _soul_ or _stream of consciousness_ in the current psychological sense. Such a mind or soul or stream of consciousness is then usually regarded as not filling a series of positions in space, and sometimes as not filling a series of positions in time. (_d_) The physical order, as thus finally constituted by the introduction of the concept of an imperceptible soul or mind, now comprises all sensible existence[117] as an aggregate of events in time and space, linked together by the principle of Causality, and exhibiting conformity with general law. To this conception recent science has made an important addition in the notion of a continuous _evolution_ or _development_ as manifesting itself throughout the series. So that we may ultimately define the physical order as a body of events occupying position in time and space, conforming to general laws with rigid and undeviating uniformity, and exhibiting continuous evolution.[118] From these general characteristics of the physical order, as conceived by current science and current popular thought, arise the fundamental problems of Cosmology. We have to discuss—(1) the real nature of material existence, _i.e._ the ultimate significance of the distinction between the two orders, and the possibility of reducing them to one; (2) the justification for the distinction between mechanical and teleological processes, and for the conception of the physical order as rigidly conformable to uniform law; (3) the leading difficulties of the conceptions of time and space, and their bearing on the degree of reality to be ascribed to the physical order; (4) the philosophical implications of the application of the notion of evolution or development to the events of the physical order; (5) finally, we ought perhaps to deal very briefly and in a very elementary fashion with the problem of the real position of descriptive physical science as a whole in its relation to the rest of human knowledge.