44. “Lastly, there are idols which have crept into men’s minds from the various dogmas of peculiar systems of philosophy, and also from the perverted rules of demonstration, and these we denominate idols of the theatre: for we regard all the systems of philosophy hitherto received or imagined, as so many plays brought out and performed, creating fictitious and theatrical worlds. Nor do we speak only of the present systems, or of the philosophy and sects of the ancients, since numerous other plays of a similar nature can be still composed and made to agree with each other, the causes of the most opposite errors being generally the same. Nor, again, do we allude merely to general systems, but also to many elements and axioms of sciences which have become inveterate by tradition, implicit credence, and neglect.”(8) Metaphysical speculation and its swarming progeny of blind and selfish political philosophies, private opinions, private “truths,” and private doctrines, sectarian opinions, sectarian “truths” and sectarian doctrines, querulous, confused and blind—such is characteristic of the _childhood_ of humanity. The period of humanity’s _manhood_ will, I doubt not, be a scientific period—a period that will witness the gradual extension of scientific method to all the interests of mankind—a period in which man will discover the essential nature of man and establish, at length, the science and art of directing human energies and human capacities to the advancement of human weal in accordance with the laws of human nature. Chapter III. Classes of Life The problems to be dealt with in this chapter are not easy, but they are exceedingly important. To classify phenomena correctly, they must be correctly analysed and clearly defined. For the sake of clearness I will use the simplest illustrations and, avoiding as much as possible the difficulties of technical terms, will use language easily to be understood by every one. In some cases the words will indeed have a technical meaning and it will be necessary to exercise great care against the danger of giving false impressions; for clear ideas are essential to sound thinking. As a matter of fact our common daily speech is ill adapted for the precise expression of thought; even so-called “scientific” language is often too vague for the purpose and requires further refining. Some may say that it is useless and unnecessary to lay so much stress on correct thinking and precise expression; that it has no practical value; for they say that “business” language is good enough to “talk business,” or to put “something over” the other fellow. But a little explanation will show that precision is often of the greatest importance.