"The man who classifies facts of any kind whatever, who sees their mutual relation and describes their sequences, is applying the scientific method and is a man of science. The facts may belong to the past history of mankind, to the social statistics of our great cities, to the atmosphere of the most distant stars, to the digestive organs of a worm, or to the life of a scarcely visible bacillus. It is not facts themselves which make science, but the method by which they are dealt with. The material of science is co-extensive with the whole physical universe, not only that universe as it now exists, but with its past history and the past history of all life therein. When every fact, every present or past phenomenon of that universe, every phase of present or past life therein, has been classified, and co-ordinated with the rest, then the mission of science will be completed."[1] Science, then, is systematic and accurate knowledge; and when we have systematic and accurate knowledge about everything there is to be known, the programme of science will be complete. This is only to say that the task it has set itself is one that will never end. So much, then, for our definitions. Religion is "an attitude to life": science is "systematic and accurate knowledge." How does the one affect the other? What are the relations between the two? That is the topic which will occupy our attention during the chapters that follow. To answer the question properly will involve a certain amount of acquaintance with the history of ideas. We must first put the preliminary question: How, as a matter of fact, have men's scientific ideas affected their religious ideas (or _vice versa_) in times past? Having tried to answer this question, we shall be in a better position to approach the religious problem as it presents itself to-day. Meanwhile a few remarks of a general character will not be out of place. It is evident that "science" can hardly fail to affect "religion." Systematised knowledge necessarily affects an individual's (or a society's) attitude to life--either by broadening and elevating that attitude, or by debasing it. Our knowledge, or what we believe to be such, tends to create certain preconceptions which make our minds hostile to certain beliefs or ideas. A man reared from his cradle on mechanical science will tend to regard miracles with suspicion; if he be logical (as he generally is not) freedom of the will, even in the most limited sense, will appear chimerical. Nor will his general attitude to life remain unaffected by his views on these points.