In this chapter Owen begins to inform his readers why it is critical to "be killing sin." He encourages the Christian to take note of not only the presence of indwelling sin, but also its constant activity. He then insists that if sin is not mortified it will produce "scandalous, soul-destroying sins." In my opinion it is in this section that (to put it into vernacular) Owen brings his A game. Consider the following:
Sin aims always at the utmost; every time it rises up to tempt or entice, might it have its own course, it would go out to the utmost sin of that kind. Every unclean thought or glance would be adultery if it could; every coveteous desire would be oppression, every thought of unbelief would be atheism, might it grow to its head (Overcoming Sin and Temptation, 53).
So Owen is saying that if sinful desires are left unchecked then they would result in the fullest manifestation of that sin. Then he goes on to tell us why this principle is so dangerous:
And herein lies no small share of the deceitfulness of sin, by which it prevails to the hardening of men, and so to their ruin (Heb. 3:13)- it is modest, as it were, in its first motions and proposals, but having once got footing in the heart by them, it constatly makes good its ground, and presses on to some father degrees in the same kind. . . This new acting and pressing forward makes the soul take little notice of what an entrane to a falling off from God is already made; it thinks all is indifferntly well if there be no futher progress; and so far the soul is made insenisble of any sin. . . but sin is still pressing forward, and that because it has no bounds but utter relinquishment of God and opposition to him. . . (Overcoming Sin and Temptation, 53).
Who of us have not experienced this phenomenon. Sin begins subtly. It does not initially tempt us to commit an adulterous act, but rather to entertain lustful thoughts. It does not begin by inviting us to murder, but rather to harbor bitterness towards another. If we do not mortify these "lesser sins" we become desentized to them. And as a result gradually it seems rather normal to complain at work, watch movies with inappropriate material or consistenly worry about life's circumstances. These sins which at one time greived our consciences now do not bother us in the least.
If you put a frog in a pot of water on the stove and immediately turn the temperature up, the frog will jump out and escape. However, if you gradually turn up the heat the frog will remain in the pot until he cooks to death. It is in this manner that sin seeks to deceive us. It attempts to lull us into believing that sin is "no big deal." It gradually elevates our sin and continues to tell us "don't worry about it." That tragedy is that if we do not rouse ourselves to mortify these practices, indwelling sin will not be content until we have renounced God himself.
The urgency of this call cannot be overstated.
Nothing can prevent this but mortification; that withers the root and strikes at the head of sin every hour. . . There is not the best saint in the world but, if he should give over this duty, would fall into as many cursed sins as ever any did of his kind (Overcoming Sin and Temptation, 53).
How do you think war could be waged against the flesh's tendency to gradually desensitize us towards our sin?