This kind of conscience is not in all men, but in such persons as are become obstinate heretics and notorious malefactors. And it is not in them by nature, but by an increase of the corruption of nature, and that by certain steps and degrees. For naturally, every man has in him blindness and ignorance of mind, are joined some remnants of the light of nature and common conscience. By practice of such sins, the light of nature is extinguished. And then comes the reprobate mind, which judges evil good and good evil. After this follows the seared conscience, in which there is no feeling or remorse. And after this comes an exceeding greediness to all manner of sin (Eph. 4:18; Rom. 1:28).
Here it may be demanded, How shall men's consciences accuse them in the day of judgment, if they are thus benumbed and seared in this life? Answer. It is said that at the last judgment all shall be brought before Christ, and that the books then shall be opened (Rev. 20:12). Among these books, no doubt, conscience is one. Wherefore, though a dead conscience in this life is as a closed or sealed book, because it does either little or nothing accuse, yet after this life it shall be as a book laid open; because God shall enlighten it, and so stir it up by His mighty power that is shall be able to reveal and discover all the sins that a man ever committed." pg. 83,84 William Perkins 'A Discourse of Conscience' The Works of William Perkins Volume 8