J. I. Packer writes:
It is a universal experience that conscience is largely autonomous in its operation; though sometimes we can suppress or stifle it, it normally speaks independently of our will, and sometimes, indeed, contrary to our will. And when it speaks, it is in a strange way distinct from us; it stands over us, addressing us with an absoluteness of authority which we did not give it and which we cannot take from it. To personify conscience and treat it as God's watchman and spokesman in the soul is not, therefore, a mere flight of fancy, it is a necessity of human experience.
J. I. Packer, A Quest for Godliness, 1990, reprint (Wheaton, IL: Crossway, 2010), 110.