With this we can all agree, but it does not bring us any nearer an "unknowable." It is perfectly true that thought can never be comprehensive enough to exhaust the possibilities of existence, since it is of the essence of thinking to limit and define. But it is a sheer impossibility to think of what lies beyond the boundary of our knowledge as unknowable, so far as we think of it at all, we must conceive it as the unknown but possibly knowable. The unknown can only be thought of thus because it is only as it is, by assumption, brought into line with what is already known that it can be thought about at all. We are compelled to think of what lies beyond the limits of our actual knowledge in the same way as a traveller thinks of the fauna and flora of an untravelled country. The new region may present many new features, but until actual observation has taken place, these new features will only be thought of as more or less unusual combinations of known animal and vegetable life. They are substantially identical with what is already known. No stranger notion ever occurred to a great thinker than that religion and science represent parallel and distinct lines of development, each having its own sphere of operation. It is all the more remarkable when we remember that with Spencer "religion" means all religion, past and present, civilised and savage. And no one is more precise in pointing out how all religious ideas find their beginnings in the conditions of primitive life. And that being the case, one wonders whether we are to picture primitive man as a profound metaphysical philosopher, speculating on that which lies behind phenomena, contemplating an "insoluble Mystery," and paying homage to an "Ultimate Reality"? Nothing could be more absurd. Thinking begins in concrete images, not in abstractions. We have only to note the development of intelligence in children to realise this. And primitive man, not being a mystic nor a metaphysician, bases his religion, not upon a reality that transcends experience, but upon a presumed fact, and what is to him the best known of all facts. And even with modern men it may safely be said that they worship God for what they believe they know about him, not because they believe him to be unknown and unknowable.