Now in order to argue it fairly and without passion or prejudice, let us pass from the subject of religious doubt and let us consider the case of doubt in other matters than religion; we all know that men have doubted in other subjects. Try then to recall to your minds the first doubt; it was only a little later than the first belief. The first instinct of the child is to believe everything, that everything he sees and hears is true. All appearances to the child are realities. The sun is to him a ball of fire that climbs up the sky, the stars are little specks of light that shine at night. The earth is a flat plain. Very soon the child learns the first great lesson of doubt, learns that things are not what they appear to be, learns to distrust appearances, learns that under the appearances there is a reality. He gets his first teaching from doubt, and all-important is the instinct of doubt. Very soon is the awakening of the sceptical part of the mental nature of man, of his understanding. The nature of the understanding is ever to ask, What and why? The spirit of doubt leads the man from question to question, from step to step, till he gets answers to his questions; he goes on from doubt to belief, and from belief to doubt, and so on to greater knowledge. Thus doubt is the means of knowledge, the instrument of discovery. Without the instinct of doubt humanity would be stagnant; with it alone humanity progresses. I do not disparage doubt, I highly value it; but doubt is useful on one condition, and one only, that it starts from a first belief. What is the cause of all this doubt and pursuit of knowledge? The supreme instinctive belief, that under all appearances there is a reality, that something underlies and causes all being; and it is the search for this essence of existence that leads the doubter on, the search of this _I am_. If he had no faith in some underlying reality beneath these phenomena, there would be no progress, and so doubt is ever seeking for that which is below what appears, and yet never reaches it.