16. I am aware that the explanation which I have given, may naturally provoke the opponents of the doctrine of scientific necessity to repeat their ordinary fundamental objections, in a form adapted to the expressions which I have used. They may say, the fact that these so-called Axioms thus become evident only during the progress of experience, proves that they are derived from experience: they may, in reply to our image, say, that truths are stuck into the mind by experience, as seeds are stuck into the ground; and that to maintain that they can grow under any other conditions, is to hold the doctrine of spontaneous generation, which is equally untenable in the intellectual and in the physical world. I shall not however here resume the general discussion; but shall only say briefly in reply, that Axioms,—for instance, this Axiom, that material substances cannot be created or annihilated by any process which we can apply,—though it becomes evident in the progress of experience, cannot be derived from experience; for it is a proposition which never has nor can be proved by experience; but which, nevertheless, has been always assumed by men, seeking for general truths, as necessarily true, and as controlling and correcting all possible experience. And with regard to the image of vegetable development, I may say, that as such development implies both inherent forms in the living seed, and nutritive powers in earth and air; so the development of our scientific ideas implies both a formative power, and materials acted on; and that, though the analogy must be very defective, we conceive that we best follow it by placing the formative power in the living mind, and in the external world the materials acted on: while the doctrine that all truth is derived from experience only, appears to reject altogether one of these elements, or to assert the two to be one.
CHAPTER XXIX.
Necessary Truth is progressive.
Objections considered.
The doctrine that necessary truth is progressive is a doctrine very important in its bearing upon the nature of the human mind; and, as I conceive, in its theological bearing also. But it is a doctrine to which objections are likely to be made from various quarters, and I will consider some of these objections.
1. Necessary truths, it will be said, cannot increase in number. New ones cannot be added to the old ones. For necessary truths are those of which the necessity is plain and evident to all mankind—to the common sense of man; such as the axioms of geometry. But that which is evident to all mankind must be evident from the first: that which is plain to the common sense of man cannot require scientific discovery: that which is necessarily true cannot require accumulated proof.
To this I reply, that necessary truths require for their apprehension a certain growth and development of the human mind. Though it is seen that they are necessarily true, this is seen only by those who think steadily and clearly, and to think steadily and clearly on any kind of subject, requires time and attention;—requires mental culture. This may be seen even in the case of the axioms of geometry. These axioms are self-evident: but to whom are they self-evident? Not to uncultured savages, or young children; or persons of loose vague habits of thought. To see the truth and necessity of geometrical axioms, we need geometrical culture.
Therefore that any axioms are not evident without patient thought and continued study of the subject, does not disprove their necessity. Principles may be axiomatic and necessary, although they require time, and the progress of thought and of knowledge, to bring them to light. And axioms may be thus gradually brought to light by the progress of knowledge.
Nor is it difficult to give examples of such axioms, other than geometrical. There is an axiom which has obtained currency among thoughtful men from the time that man began to speculate about himself and the universe:—E nihilo nil fit: Nothing can be made of nothing. No material substance can be produced or destroyed by natural causes, though its form and consistence may be changed indefinitely. Is not this an axiom? a necessary truth? Yet it is not evident to all men at first, and without mental culture. At first and before habits of steady and consistent thought are formed, men think familiarly of the creation and destruction of matter. Only when the mind has received some philosophical culture does it see the truth and necessity of the axiom of substance, and then it does see it.
And the axioms on which the science of mechanics rests, that the cause is measured by the effects, that reaction is equal and opposite to action, and the like,—are not these evident to a mind cultivated by steady thought on such subjects? and do they not require such culture of the mind in order to see them? Are they not obscure or uncertain to those who are not so cultured, that is to common thinkers: to the general bulk of mankind? Thus then it requires the discipline of the science of mechanics to enable the mind to see the axioms of that science.
And does not this go further, as science and the careful study of the grounds of science go further? To a person well disciplined in mechanical reasoning it has become, not a conclusion, but a principle, that in mechanical action what is gained in power is lost in time: or that in any change, the force gained is equal to the force lost, so that new force cannot be generated, any more than new matter, by natural changes. Is this an axiom? a necessary fundamental truth? It appears so to at least one great thinker and discoverer now alive among us. If it do not appear so to us, or not in the same sense, may not this be because we have not yet reached his point of view? May not the conviction which is now his alone become hereafter the conviction of the philosophical world? And whatever the case may be in this instance, have there not been examples of this progress? Did not Galileo and the disciples of Galileo reduce several mechanical principles to the character of necessary truths, after they had by experiment and reasoning discovered them to be actually true? And have we not in these cases so many proofs that necessary truth is progressive, along with the progress of knowledge?