New truth appears to be usually derived from new physical or mental experiences of phenomena external to our perceiving faculty; either by observing matter or its forces under new conditions or from a new aspect; and the knowledge comes to us either through the avenues of our feelings and senses, or by means of direct observations, by comparison of such impressions, or by inferences drawn from them. From the results of such mental operations, additional new truths are evolved by the more complex process of analysis, combination and permutation of ideas. New truths are also evolved from old ones by each of these latter methods; but sooner or later the implicit contents of our stock of old knowledge becomes exhausted when used for such a purpose, and we are then obliged to seek new experience. As new truths may be acquired in the more direct manner, by acquisition of new experience; and less directly, by mental operations upon old ideas, other subjects of less fundamental and more concrete nature than the simple sciences, such as sociology, &c., are also sources of progress, when treated in these ways. {164} Of all subjects, the simple sciences of physics and chemistry, are at the present time, apparently making the most rapid advance, and the chief reasons for this probably are, _1st._ they treat of facts and principles which can be verified, and _2nd._ because the more complex sciences, together with the arts and manufactures based upon them, can only improve in proportion as they are developed. All the essentially human subjects, such as sociology, politics, morality, religious worship, &c., are in this position, and are probably results partly of the operation of the great principles of nature acting through the body and mind of man. The chief method of discovering new truth is that of observation, experiment, and study, and further mental treatment of the results. The most systematic methods also of evolving new truths are those employed by scientific men in making discoveries, and when any person arrives at a new idea, he usually (either consciously or unconsciously) employs them. The acquisition of new knowledge must of necessity precede its diffusion. Immediately a new truth, especially an important one, is discovered, its influence begins to permeate the existing mass of knowledge in various directions, causing us to view many of our old ideas in a new aspect; giving rise also by comparison and inference, and by processes of combination, permutation and analysis of ideas, to a multitude of other new truths, usually less important ones, which themselves also affect previous knowledge in similar ways, {165} and by analogous treatment give rise to additional new conceptions.