The Scripture informs us they (ie fears) have been of as ancient a date as the revolt of the first man, (Gen. 3:10): “I was afraid,” saith Adam, “because I was naked” which was an expectation of the judgment of God. All his posterity inherit his fears, when God expresseth himself in any tokens of his majesty and providence in the world. Every man’s conscience testifies that he is unlike what he ought to be, according to that law engraven upon his heart. In some, indeed, conscience may be seared or dimmer; or suppose some men may be devoid of conscience, shall it be denied to be a thing belonging to the nature of man? Some men have not their eyes, yet the power of seeing the light is natural to man, and belongs to the integrity of the body. Who would argue that, because some men are mad, and have lost their reason by a distemper of the brain, that therefore reason hath no reality, but is an imaginary thing? But I think it is a standing truth that every man hath been under the scourge of it, one time or other, in a less or a greater degree; for, since every man is an offender, it cannot be imagined, conscience, which is natural to man, and an active faculty, should always lie idle, without doing this part of its office. The apostle tells us of the thoughts accusing or excusing one another, (or by turns,) according as the actions were. Nor is this truth weakened by the corruption in the world, whereby many have thought themselves bound in conscience to adhere to a false and superstitious worship and idolatry, as much as any have thought themselves bound to adhere to a worship commanded by God. This very thing infers that all men have a reflecting principle in them; it is no argument against the being of conscience, but only infers that it may err in the application of what it naturally owns. We can no more say, that because some men walk by a false rule, there is no such thing as conscience, than we can say that because men have errors in their minds, therefore they have no such faculty as an understanding; or because men will that which is evil, they have no such faculty as a will in them.
The Existence and Attributes of God - The existence of God