The term "oppose themselves" in the King James Version is actually one word in the Greek, and it is translated in most modern versions as "those who are in opposition," that is, to sound doctrine and practice. The interesting thing is that the King James Version is also correct. The Greek word is capable of being interpreted either way. There is a real difference in them, however. The sense of one is outward, opposing certain things or people, while the sense of the other is toward the self, which is how the King James translators chose to translate it.

Either way, the word connotes some measure of division, disunity, or opposition, either toward doctrine or with others in the congregation for whatever reason. Regardless, the consequence is destructive; division destroys. In terms of the King James translation—"oppose themselves"—the division is within the self and destructive to the self.

Paul, then, is informing us that those who disagree with the doctrine of Christ actually oppose themselves because in the end truth will prevail, and those who disagree with the doctrine will bring the penalties of opposition to Christ upon themselves. It is like shooting oneself in the foot, or in this case, ultimately in the heart, because truth cannot be broken without some consequence, unless it is repented of.

Division in the mind actually causes us to fight against our own best interests. For example, we will spend our income foolishly on trivialities, taking ourselves into debt and putting ourselves under the painful obligation of paying it off with interest, which is in reality a form of slavery. Because the mind is divided between wisdom and foolishness, people like this (and it includes all of us to some degree) go nowhere profitable until they get their minds harnessed and headed in a wise direction.