This is Conscience; and, from the nature of the case, its very existence carries on our minds to a Being exterior to ourselves; for else whence did it come? and to a Being superior to ourselves; else whence its strange, troublesome peremptoriness? I say, without going on to the question what it says, and whether its particular dictates are always as clear and consistent as they might be, its very existence throws us out of ourselves, and beyond ourselves, to go and seek for Him in the height and depth, whose Voice it is. As the sunshine implies that the sun is in the heavens, though we may see it not, as a knocking at our doors at night implies the presence of one outside in the dark who asks for admittance, so this Word within us, not only instructs us up to a certain point, but necessarily raises our minds to the idea of a Teacher, an unseen Teacher: and in proportion as we listen to that Word, and use it, not only do we learn more from it, not only do its dictates become clearer, and at its lessons broader, and its principles more consistent, but its very tone is louder and more authoritative and constraining. And thus it is, that to those who use what they have, more is given; for, beginning with obedience, they go on to the intimate perception and belief of one God. His voice within them witnesses to Him, and they believe His own witness about Himself. They believe in His existence, not because others say it, not in the word of man merely, but with a personal apprehension of its truth. This, then, is the first step in those good dispositions which lead to faith in the Gospel.
PPS 2/2 rewitten for Sermons on various occasions, sermon 5.