It may be as impossible for man to prove the trustworthiness of his intellectual faculties as it is for the bee to prove the truth of its marvellous instinct; but, in either case, the reason may be that any such proof is unnecessary, that it is superseded by the laws of Instinct in the one, and by the laws of Thought in the other, and that by these laws a better and surer provision is made for our guidance than any that could have been found in a mere logical faculty,--a natural and irresistible authority, which the Skeptic may dispute, but cannot destroy, and which, however disowned in theory, must be practically obeyed.
It must be evident that the _various meanings_ which have been attached to the term Certitude must materially affect both the statement and solution of the general problem, and, more particularly, that they must have an important bearing on the question, whether the doctrine which affirms the Being, Perfections, and Providence of God, should be ranked under the head of _certain_, or only of _probable_, truth.

If, in making use of the term Certitude, I mean to denote by it something different from the certainty which belongs to the most assured convictions of the human mind, something that arises, not from the spontaneous and direct exercise of its faculties, but from a process of reflective thought or philosophical speculation, something, in short, that is peculiar to the metaphysical inquirer, and is not the common heritage of the race at large; then, unquestionably, the problem, as thus understood, must leave out of view many of the surest and most universal beliefs of mankind,--beliefs which may be illustrated and confirmed by Philosophy, but which are anterior to it in respect to their origin, and independent of it in respect of the evidence on which they severally rest.

In the case of Certitude, just as in the case of every similar term expressive of a simple, elementary idea, the ultimate appeal must be made to individual consciousness.

No one can convey to another a conception of Certitude by means of words, apart from an experimental sense of it in the mind of the latter, any more than he could give the idea of color to the blind or of music to the deaf.

It is because we have had experience of it in our own breasts that we recognize and respond to the descriptions which others give of it.