All the facts mentioned in this chapter, and the various points of essential similarity between physical, physiological, and mental phenomena, justify the conclusion that both moral and other mental actions, like physical and chemical ones, are obedient to the great principles of science. And from the evidence here adduced and alluded to, it is certain that those principles influence human progress, not only in a few conspicuous direct ways, but in a multitude of varied, deep-seated, and indirect ones. If the statements made in this Chapter are true, that the innate properties of matter really are motive powers of the human organism, and the principles of science are regulators of mental and moral action; that Man is a feeble epitome of the principles and powers of inorganic matter; that the laws of Nature operate in utter disregard of his erroneous beliefs; that nearly all man's sins and sufferings are traceable to his ignorance and limited powers; that in proportion to his ignorance of science so is he unable to foresee the more remote consequences of his thoughts and acts; and if new knowledge does correct erroneous beliefs and purify human thought and action, it behoves teachers of morality to make themselves adequately acquainted with the principles and newest developments of science. * * * * * {157} CHAPTER III. ------ NEW TRUTH, AND ITS GENERAL RELATION TO HUMAN PROGRESS. The great source of the success of applying science to trade, and of the beneficent effect of science upon human welfare in general, is simply the influence of demonstrable truth. We know that if we have once discovered all the principles, laws, and conditions of some scientific phenomenon, or of some improved process or result in a manufacture, the reproduction of exactly the same conditions will hereafter enable us to invariably produce the same result. In this respect science differs from dogma, the truth or falsity of which cannot be demonstrated; it also differs from empiricism, because when empirically working a process we are ignorant of the principles or laws which are operating, whilst with a scientific knowledge we understand those laws, and can direct them to our particular purposes. In the process of electro-plating for example, we understand the laws of the phenomena, and can direct them so as to obtain silver of a hard or soft quality, brittle or tough, crystalline silver, &c., according to our wish; but if we had only an empirical knowledge of the subject we could not thus vary the process. {158}