[Footnote 25: The need of a language of rigid mathematical precision for the purposes of philosophic thought and discussion has long been the subject of remark. Hence Bishop Wilkins's Essay toward a real character and a philosophic language (1668), and the earlier Ars Signorum of George Dalgarno--boldly presented by its inventor as a "remedy for the confusion of tongues, as far as this evil is reparable by art." We may give these ingenious authors full credit for the excellent intentions with which they set out on impossible undertakings. A philosophic language may perhaps be attained in the millennium, but then probably it will be no longer needed. Meanwhile readers interested in the history of the mad scheme called Volapük may find some curious matter in these rare works.] Bacon notes two ways particularly in which words impose on the understanding--they are employed sometimes "for fantastic suppositions ... to which nothing in reality corresponds," and sometimes for actual entities, which, however, they do not sharply, correctly, and completely describe. The eighteenth century speculated at length on a state of Nature and the social contract, unaware that it was deluding itself with unrealities, and we have not yet done with such abstractions as the Rights of Man, Nature (personified), Laws of Nature (conceived as analogous to human laws), and the Vital Principle. The more common and serious danger of language, however, lies in the employment of words not clearly or firmly grasped by the speaker or writer--words which, in all probability, he has often heard and used, and which he therefore imagines to represent ideas to him, but which, closely analyzed, will be found to cover paucity of knowledge or ambiguity of thought. Cause, effect, matter, mind, force, essence, creation, occur at once as examples. Few among those who so glibly rattle them off the tongue have ever taken the trouble to inquire what they actually mean to them, or whether, indeed, they can translate them into thought at all.