Referring again to the sources of this witness, to which we have just now briefly alluded, we remark more particularly, that the nature of the human mind is such, that it bears, as it were, the idea of a Supreme Being, and other truths, closely connected with the idea of a Supreme Being, written on its very structure. It is a psychological fact, which a careful observation of the progress of human culture has fully demonstrated, that the human mind, when brought into full and unperverted action, always develops the idea of a God. It is an idea written there in letters uneffaceable; and, though sometimes obscured and deeply hidden, it will always come out and make itself evident, when it is brought to the light. And there too, essential in the structure of the same mind, are the conceptions of truth and justice, of sympathy and benevolence as due from man to his fellow-man, of immutable wrong and immutable right. There is no barbarism so low, so linked to the extreme of moral degradation, where these bright conceptions, in connection with their related emotions, do not exist in greater or less distinctness. The mind, therefore, by its very nature, by a voice which cries out unceasingly from its depths, bears witness for God. Were it not so, heathenism, still more degraded and destitute than it is at present, would have heard no announcement from its moral teachers; would have had no Socrates, no Plato.
The world, of which we are a part, and the systems of worlds with which we are connected, bear witness for God. There is not a tree nor a flower, no river, nor lake, nor cataract, no hill, nor valley, nor mountaintop, nothing on the earth nor under the earth, neither the fruits it bears on its surface nor the minerals it cherishes in its bosom, no insect, nor bird, nor quadruped, nor any other thing of the infinite varieties presented to our notice, which, on a careful examination in itself and its relations, does not bear its testimony.
— The Life of Faith (1852) Part 1, Chapter 4.