In commencing a course of lectures on Mental Science, it is somewhat difficult for the lecturer to fix upon the best method of opening the subject. It can be approached from many sides, each with some peculiar advantage of its own; but, after careful deliberation, it appears to me that, for the purpose of the present course, no better starting-point could be selected than the relation between Spirit and Matter. I select this starting-point because the distinction - or what we believe to be such - between them is one with which we are so familiar that I can safely assume its recognition by everybody; and I may, therefore, at once state this distinction by using the adjectives which we habitually apply as expressing the natural opposition between the two - living spirit and dead matter. These terms express our current impression of the opposition between spirit and matter with sufficient accuracy, and considered only from the point of view of outward appearances this impression is no doubt correct. The general consensus of mankind is right in trusting the evidence of our senses, and any system which tells us that we are not to do so will never obtain a permanent footing in a sane and healthy community. There is nothing wrong in the evidence conveyed to a healthy mind by the senses of a healthy body, but the point where error creeps in is when we come to judge of the meaning of this testimony. We are accustomed to judge only by external appearances and by certain limited significances which we attach to words; but when we begin to enquire into the real meaning of our words and to analyse the causes which give rise to the appearances, we find our old notions gradually falling off from us, until at last we wake up to the fact that we are living in an entirely different world to that we formerly recognized. The old limited mode of thought has imperceptibly slipped away, and we discover that we have stepped out into a new order of things where all is liberty and life. This is the work of an enlightened intelligence resulting from persistent determination to discover what truth really is irrespective of any preconceived notions from whatever source derived, the determination to think honestly for ourselves instead of endeavouring to get our thinking done for us. Let us then commence by enquiring what we really mean by the livingness which we attribute to spirit and the deadness which we attribute to matter.