What foundation has faith in human authority? Most men are ignorant of the philosophical reasons which may be assigned; but their faith is not therefore less lively than that of philosophers. But why is this so? Because there is a necessity, and at its side an instinct to be satisfied. Man must believe in man, and he believes. And here note well, that the greater the necessity, the greater the faith. The very ignorant and imbecile believe all that is told them; they make other men their guide, and blindly follow them. The tender child, knowing nothing, abandons itself to the absolute belief of the greatest marvels: the word of those around is to it an invaluable criterion of truth.
322. Besides the cases of first intellectual and moral principles, the objectiveness of ideas and sensations, the weight of human authority, man must give his instantaneous assent to certain truths, which, although he might, had he the time, demonstrate, he cannot now, because so suddenly are they presented to him, that they exact an immediate formation of judgment, and, sometimes, also action. In all these cases, there is a natural inclination impelling us to assent.
Hence it is that we instinctively judge it impossible, or little less than impossible, to cause a determinate effect, by a fortuitous combination; as, for example, to form a page of Virgil by a chance mixture of types, or to hit the bull's eye of a target without taking aim, and other similar things. In this there is assuredly a philosophical reason, but one not known to common people. There is evidence of this reason in the theory of probabilities: it is a distinct application of the principle of causality, and of the natural opposition of our understanding to supposing an effect without a cause, and order where there is no ordering intelligence.
323. Arguments of analogy, are in human life necessary in infinite cases. How do we know that the sun will rise to-morrow? By the laws of nature. How do we know that these will continue in force? Evidently, we must finally recur to analogy. The sun will rise to-morrow, because it has risen to-day; it rose yesterday, and it has never failed to rise. How do we know that spring will again bring flowers, and autumn fruits? Because it has so happened in former years. Men ordinarily do not know the reasons which might be given for founding the argument from analogy on the constancy of the laws of nature, and on the relation between certain physical causes and determinate effects; but their assent is required and given.
324. In all the cases cited, excepting, perhaps, that of immediate evidence, the inclination to assent may be, and really is, called common sense. The reason of this exception is, that in this case, although there is no demonstration, the predicate is nevertheless most clearly seen contained in the idea of the subject; but in the other cases there is neither demonstration nor this vision. Man assents by a natural impulse; and if any thing is objected to his belief, he does not call attention to his conception, as in immediate evidence, but is completely disconcerted, and knows not what to answer; he then applies to the objection, not the name of error, nor of absurdity, but that of extravagance, of something contrary to common sense.
Suppose, for example, a little grain of sand to be mixed with a great heap, and some one to come and say: I will put my hand into the heap, and instantly draw out the one grain hidden there. What will you object to such a one? What will the beholders reply? Nothing; or, looking at each other in perfect surprise, they will exclaim: "What extravagance! He has no common sense!" Or suppose some one to say, that all we see is nothing, that there is no external world, that we have no body, or that all told us of the existence of a city called London is untrue. Whoever hears such madness, knows not what to answer; but he repels it by a natural impulse, and the mind feels that this is nonsense without stopping to examine.
325. We shall now inquire whether common sense be a certain criterion of truth, whether it be so in all, or in what cases, and what characters it must have in order to be an infallible criterion.
Man cannot lay aside his nature: when it speaks, reason will not allow it to be ignored. A natural inclination, simply because it is natural, is in the eyes of philosophy something highly respectable: it is the province of reason and free will not to allow it to go astray. What is natural to man is not always so perfectly fixed as it is in brutes, where instinct is blind as it must be, where there is neither reason nor free will. The exercise of man's natural inclinations is subordinate to his reason and free will, and, consequently, when these are called instincts, the word has a very different meaning from what it has when applied to brutes. What happens in the moral order is also verified in the intellectual. We have not only our heart to watch, but also our understanding; both are subject to the law of perfectibility; the objects which they offer to us are good and evil, truth and error. Nature herself shows us which one we ought to choose, but does not force our choice; life and death are before us, we may select the one we please.
326. There is in man, independently of the action of free will, a quality which oftentimes has the effect of turning his natural inclinations from their object; it is weakness. Hence, it is nothing extraordinary for these inclinations to be so distorted as to lead to error instead of truth, and this renders it necessary to determine what characters common sense should have, in order to be an absolutely infallible criterion.
327. We will point out the conditions, such as we conceive them to be, of true and never-erring common sense.