Commenting further on Westminster Confession of Faith, chapter 6 Hodge writes,
"Now, although we cannot explain precisely the origin of sin in the holy soul of Adam, it is plain that the difficulty lies only in our ignorance. We have none of us experienced the same condition of free agency as those which give characer to the case of Adam. We have always been under the bondage of corruption, except in so far as we are momentarily assisted against nature by supernatural grace. Now, in order that a volition shall be holy, it must spring from a positively holy affection or disposition; and as these are not native to our hearts, we cannot exercise holy volitions without grace. But Adam was in a state of probation, holy yet fallible. Saints and angels are holy and infallible, yet their infallibility is not essential to their natures but is a superadded divine grace sustained by the direct power of God. While holiness must always be positive, rooting itself in divine love, it is plain that sin may originate in defect; not in positive alienation, but in want of watchfulness - in the temporary ascendency of the natural and innocent appetites of the body or constitutional tendencies of the soul of the higher powers of conscience" (my emphasis). Westminster Confession of Faith: A Commentary. A.A. Hodge, pp. 106-107.