I have dealt in the sixteenth chapter of the _Riddle_ with the important question of the relations of knowledge and faith. But I must return to the subject here, as what I said has given rise to a good deal of misunderstanding and criticism. I by no means claimed, as my opponents allege, to "know everything," or to have solved every problem. In fact, I said repeatedly that there are narrow limits to our knowledge, and always will be. I had also expressly stated that the irresistible impulse to learn in the intelligent man, or reason's constant demand to know causes, presses us to fill up the gaps in our knowledge by faith. But I had at the same time pointed out the contrast between scientific (natural) and religious (supernatural) faith. The one leads us to form hypotheses and theories; the other ends in myths and superstition. Scientific faith fills the gaps in our knowledge of natural law with temporary hypotheses; but mystic religious faith contradicts natural law, and transcends its limits in the form of a belief in miracles. The great triumph of the progress of science in the nineteenth century, its theoretical value in the formation of a rational philosophy of life, and its practical value on the various sides of modern civilization, consist, above all, in the absolute recognition of fixed natural laws. That relation of things to each other, which we call causation, makes it possible for us to understand and explain facts. We feel that our thirst for a knowledge of the causes of things is contented when science points out the "sufficient reason" of them. In the whole province of inorganic cosmology natural law is now generally recognized to be all-powerful; in astronomy, geology, physics, and chemistry all phenomena are reduced to fixed laws, and in the long-run to the all-embracing law of substance, the great law of the conservation of matter and force (_Riddle_, chapter xii.).