These two questions have not been always clearly distinguished; the relativity of knowledge has been sometimes confounded with uncertainty. The untutored mind is apt to suppose that objects exist independently of the human faculties, because they really exist independently of the faculties of any individual. In the same way, knowledge appears to be a body of truths stored up in books, which when once ascertained are independent of the discoverer. Further consideration shows us that these truths are not really independent of the mind; there is an adaptation of one to the other, of the eye to the object of sense, of the mind to the conception. There would be no world, if there neither were nor ever had been any one to perceive the world. A slight effort of reflection enables us to understand this; but no effort of reflection will enable us to pass beyond the limits of our own faculties, or to imagine the relation or adaptation of objects to the mind to be different from that of which we have experience. There are certain laws of language and logic to which we are compelled to conform, and to which our ideas naturally adapt themselves; and we can no more get rid of them than we can cease to be ourselves. The absolute and infinite, whether explained as self-existence, or as the totality of human thought, or as the Divine nature, if known to us at all, cannot escape from the category of relation. But because knowledge is subjective or relative to the mind, we are not to suppose that we are therefore deprived of any of the tests or criteria of truth. One man still remains wiser than another, a more accurate observer and relater of facts, a truer measure of the proportions of knowledge. The nature of testimony is not altered, nor the verification of causes by prescribed methods less certain. Again, the truth must often come to a man through others, according to the measure of his capacity and education. But neither does this affect the testimony, whether written or oral, which he knows by experience to be trustworthy. He cannot escape from the laws of his own mind; and he cannot escape from the further accident of being dependent for his knowledge on others. But still this is no reason why he should always be in doubt; of many personal, of many historical and scientific facts he may be absolutely assured. And having such a mass of acknowledged truth in the mathematical and physical, not to speak of the moral sciences, the moderns have certainly no reason to acquiesce in the statement that truth is appearance only, or that there is no difference between appearance and truth.