What, then, is this central principle which is at the root of all things? it is life. but not life as we recognise it in particular forms of manifestation; it is something more interior and concentrated than that. it is that "unity of the spirit" which is unity, simply because it has not yet passed into diversity. perhaps this is not an easy idea to grasp, but it is the root of all scientific conception of spirit; for without it there is no common principle to which we can refer the innumerable forms of manifestation that spirit as- sumes.