But there is yet another thought which seems to have escaped such a thinker: the possibility of the co-existence of more than one world and of life passing from one world to another. Mathematicians have already shown the possibility of this by discussing the existence of a fourth dimension, and even working out problems involving the assumption of the existence of this fourth dimension. The suggestion has been made especially easy to grasp in the remarkable anonymous romance "Flatland," published some thirty years ago, which pictures the world of two dimensions, wherein one person gets the notion of the existence of a third dimension, and the extraordinary results that follow his heresy, or madness, as it seems to his less enlightened fellows. If the theory of the existence of another, or other dimensions be a tenable one, we can conceive of the existence of a number of worlds around us, co-existing with our own and including it, of which we are either wholly unconscious or only very dimly conscious, and that not by the faculties by means of which we have knowledge of our own world. Now if we suppose that somewhere within us, at the centre of our lives, is some meeting-point, some door through which we may have contact with these other worlds and pass out into them, [p.122] we can also conceive of a development growing out from this point of contact into that larger life of which we should necessarily remain unconscious here, or even if our whole nature were suddenly to be filled by a consciousness of how its life extended beyond this universe into those other worlds, we should yet be unable to express in terms of our own world this wider life, or could only express it by symbols. The incapacity of our friends to understand our experience would be no proof that it was not true, nor would our own inability to express it in any way lessen the reality of that experience to us. If such a hypothesis be correct, what may happen at death may be that we pass out of the narrower world of three dimensions into the wider world, which includes this and much more. Another way of looking at the problem has been to conceive of our various senses as channels through which we have entered into communication with the world without us. At present we most of us are only conscious of five such channels. We may conceive of the possibility of many other channels of which we have no experience (and indeed observation of certain living creatures has already led to the hypothesis of a sixth sense, different from any of our own), and we can also think of the channels as being one by one closed. So that at death we may conceive of all our existing lines of communication with the outer world being removed, and wholly new channels, with [p.123] what may seem like an entirely different world, being opened up.[29] <#_edn29>