One sphere of thought where the thinker is compelled to be original; where it is practically impossible for him to fall into beaten tracks, is invention. But there is useless as well as useful invention. A man’s ambition may range all the way from inventing a machine to harness directly the limitless power of the sun, down to devising a tenacious tip for shoelaces. But he should be careful about inventing something already patented. He should be even more careful to avoid inventing something for which there is no demand. One of Edison’s first patents was for a machine to register quickly the votes of legislative assemblies. And it worked. But the legislative assemblies didn’t want it, because they didn’t want their votes quickly registered. That would have ended good old filibuster methods. Another invention of great uselessness which has been several times attempted is a machine to write words just like the human hand writes them. There are really so many useful things which do not exist and for which there is a demand, that it seems quite a pity nine out of ten patents in the files at Washington are for things inutile. If the would-be inventor cannot himself think of something really needed, almost any big patent attorney house will send him an entire book of suggestions on “What to Invent.” Invention usually requires highly technical knowledge, not to speak of facilities for experiment and a well-supplied purse. But nothing gives more solid satisfaction to its creator than a successful appliance. While the conscientious philosopher is constantly harassed by doubts as to whether, after all, he has discovered truth; the inventor need not worry. His machine either works or it does not work, and he _knows_ the truth of his thought thereby. On the other hand the philosopher will always have _some_ thoughts. Be they true or not they may at least be interesting and worth recording, whereas the inventor may toil on for years and years with absolutely nothing to show for his exertion at the end. . . . There are a number of problems that are not of great “practical” importance, but whose theoretic value is so transcendent as to compel attention. Among these are certain problems in psychology, but more especially in metaphysics, philosophy and even religion, insofar as religion can be said to have problems. _Is there a God and is it possible for man to learn anything of His nature?_ Some readers may object to the first part of this question. But I state it because I am anxious to avoid dogmatism. _Is the soul immortal?_ What do we mean by the soul? Does science disprove the life after death? _What is the test of truth?_ How shall we know truth when we have it? What after all is “truth”?