The real source of all that is good in new scientific knowledge arises from its verified and verifiable character, its high degree of certainty, and its capacity of withstanding all the tests which can be applied to it. By the term "scientific knowledge" in this case I mean that only that which has been verified, and I purposely exclude all matters of hypothesis, mere opinion or belief. Scientific research is the chief basis of national progress, not only because it is continually disclosing new truths to us, but also because the truths it reveals are frequently of the most definite kind.
As the term "verified truth" may appear vague, the questions may well be asked, what is truth? And how may we best detect it? And especially what is new truth? and how may it best be recognised? Truth may be conveniently defined as universal consistency; or that which perfectly conforms to facts, and agrees with the widest experience, when tested by means of all our intellectual powers, the reasoning faculty in particular. The usual modern criterion of it, is consistency with the fundamental axioms of logic, and with all the great principles of nature as established by means of scientific research, such as the universality of causation, the continuity of phenomena, the indestructibility of matter and energy, the convertibility and equivalency of forces, &c. All truth whatever is one in character by possessing the inseparable attribute of complete consistency. The truthfulness of scientific knowledge is proved by its agreement with universal experience and with the
fundamental logical axioms:—a thing either is or is not:—a thing cannot both be and not be:—a thing must either be or not be:—things equal to the same are equal to each other; &c. It is chiefly by means of knowledge of these axioms and of the above principles of science, and of their varied and numerous modes of operation and application, that the man of science "explains" the multitudinous phenomena of nature, predicts future events, and is enabled to discover new truths and develope new inventions in the arts. Unlike other persons; when he sees a new effect, or hears of a new phenomenon, he at once refers it to these principles, in order to test its correctness or to explain it.
With regard to the detection of truth, that is often a difficult and complex process. There exists no royal or easy method; usually it can only be recognised by means of laborious and critical examination of the whole of the evidence obtainable in the case; and even then we are often obliged to be satisfied with only an approximation, or it may be with even a mere probability. Frequently also the truthfulness or otherwise of a statement cannot be decided in any degree in consequence of the absence of suitable or sufficient evidence, and for that we may have to wait for ages. We are now waiting for evidence necessary to decide many questions respecting the human mind.
With regard to the question, what is new truth?; that also is a difficult one to solve. The forms in which different truths appear are so various, and those
also in which even the same truth may shew itself are so diverse, that it is often impossible to discriminate new truth from old ideas clothed in a new form of words. The newness of an idea is entirely a question of evidence, and to determine it, usually requires a complete knowledge of all the circumstances affecting the particular case.
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.