You never hear the really philosophical defenders of the doctrine of uniformity speaking of _impossibilities_ in nature. They never say, what they are constantly charged with saying, that it is impossible for the builder of the universe to alter His work. Their business is not with the possible, but the actual; not with a world which _might_ be, but with a world which _is_. This they explore with a courage not unmixed with reverence, and according to methods which, like the quality of a tree, are tested by their fruits. They have but one desire—to know the truth. They have but one fear—to believe a lie. And if they know the strength of science, and rely upon it with unswerving trust, they also know the limits beyond which science ceases to be strong. They best know that questions offer themselves to thought which science, as now prosecuted, has not even the tendency to solve. They keep such questions open, and will not tolerate any unlawful limitation of the horizon of their souls. They have as little fellowship with the atheist who says there is no God as with the theist who professes to know the mind of God. “Two things,” said Immanuel Kant, “fill me with awe: the starry heavens and the sense of moral responsibility in man.” And in his hours of health and strength and sanity, when the stroke of action has ceased and the pause of reflection has set in, the scientific investigator finds himself overshadowed by the same awe. Breaking contact with the hampering details of earth, it associates him with a power which gives fulness and tone to his existence, but which he can neither analyze nor comprehend. ------------------------------------------------------------------------ ● Transcriber’s Notes: ○ The first 44 footnotes are gathered together in the “NOTES AND REFERENCES” section. The following footnotes appear in the text where they are referenced. ○ The mid dot—“·” is used in numbers to separate the whole part from the decimal fraction of the number. ○ Missing or obscured punctuation was silently corrected. ○ Typographical errors were silently corrected. ○ Inconsistent spelling and hyphenation were made consistent only when a predominant form was found in this book. ○ Text that was in italics is enclosed by underscores (_italics_). ○ The use of a caret (^) before a letter, or letters, shows that the following letter or letters was intended to be a superscript, as in S^t Bartholomew or 10^{th} Century. ○ Superscripts are used to indicate numbers raised to a power. In this plain text document, they are represented by characters like this: “MV^2” or “10^{18}”, i.e. MV squared or 10 to the 18th power.