Nevertheless, changes take place and are cumulative in character. Observation of them in the light of their recognized consequences arouses reflection, discovery, invention, experimentation. When a certain state of accumulated knowledge, of techniques and instrumentalities is attained, the process of change is so accelerated, that, as to-day, it appears externally to be the dominant trait. But there is a marked lag in any corresponding change of ideas and desires. Habits of opinion are the toughest of all habits; when they have become second nature, and are supposedly thrown out of the door, they creep in again as stealthily and surely as does first nature. And as they are modified, the alteration first shows itself negatively, in the disintegration of old beliefs, to be replaced by floating, volatile and accidentally snatched up opinions. Of course there has been an enormous increase in the amount of knowledge possessed by mankind, but it does not equal, probably, the increase in the amount of errors and half-truths which have got into circulation. In social and human matters, especially, the development of a critical sense and methods of discriminating judgment has not kept pace with the growth of careless reports and of motives for positive misrepresentation. What is more important, however, is that so much of knowledge is not knowledge in the ordinary sense of the word, but is “science.” The quotation marks are not used disrespectfully, but to suggest the technical character of scientific material. The layman takes certain conclusions which get into circulation to be science. But the scientific inquirer knows that they constitute science only in connection with the methods by which they are reached. Even when true, they are not science in virtue of their correctness, but by reason of the apparatus which is employed in reaching them. This apparatus is so highly specialized that it requires more labor to acquire ability to use and understand it than to get skill in any other instrumentalities possessed by man. Science, in other words, is a highly specialized language, more difficult to learn than any natural language. It is an artificial language, not in the sense of being factitious, but in that of being a work of intricate art, devoted to a particular purpose and not capable of being acquired nor understood in the way in which the mother tongue is learned. It is, indeed, conceivable that sometime methods of instruction will be devised which will enable laymen to read and hear scientific material with comprehension, even when they do not themselves use the apparatus which is science. The latter may then become for large numbers what students of language call a passive, if not an active, vocabulary. But that time is in the future.