The responsibilities listed so far present two opposite ways of life: the way of the Spirit and the way of the sinful nature. The absolute contrast between these alternatives has been developed throughout Paul's ethical appeal. Now it is the hour of decision. Now his readers must consider very carefully the consequences of choosing one way or the other. They cannot drift; they cannot remain neutral; they must decide whether they are going to walk by the Spirit or gratify the desires of their sinful nature. Since each individual must decide for himself or herself which way to live, Paul puts his challenge in a singular form.

Paul introduces his call for decision with a solemn warning based on an agricultural principle: Do not be deceived: God cannot be mocked. A man reaps what he sows (v. 7). When people think and act as if they will not reap what they have sown, or as if they will reap something different from what they have sown, they are deceiving themselves and mocking God. But since the inexorable law of reaping what is sown has always been proved true, the proverbial statement of warning God cannot be mocked is also true: no one can mock God and get away with it.

Yet there is a common tendency to think that there is one exception to this universal principle: "Though it proves true for everyone else, it is not true for me. I will not have to reap a harvest from the seeds I sow. I can sow whatever seed I want and still expect a good harvest." This common line of thought only proves the words of the prophet Jeremiah, "The heart is deceitful above all things and beyond cure" (Jer 17:9). Our capacity for self-deception is frightening. It is amazing how blind otherwise brilliant people can be to their own spiritual direction in life. In fact, the more brilliant people are, the more skilled they are at developing rationalizations to deceive themselves and to hide from God. The story of Adam and Eve's hiding from God behind their skimpy clothes and even skimpier excuses is our common human experience. Paul's warning needs to be heard, and to be heard often, to warn us against our most brilliant self-delusions.

Paul then applies the agricultural principle of reaping what is sown: The one who sows to please his sinful nature, from that nature will reap destruction; the one who sows to please the Spirit, from the Spirit will reap eternal life (v. 8). Here we are faced with a decision, a decision that determines our destiny. We are not victims of fate, bad luck or even predestination. Our destiny is determined by our decision: shall we sow to the sinful nature or to the Spirit? The old proverb is true: "Sow a thought, reap an act; sow an act, reap a habit; sow a habit, reap a character; sow a character, reap a destiny."

Those who are sowing to please the sinful nature are destroying relationships with others: they are biting, devouring, provoking and envying others (5:15, 26). In their arrogance they are seeking to pressure everyone to conform to the same ethnic customs and traditions. Churches are being torn apart and destroyed by ethnic rivalries and social competition. Sowing to please the sinful nature will always result in a harvest of destruction, a destruction of relationships with others and with God.

Sowing to please the Spirit means "serving one another in love" (5:13), restoring one who has been caught in sin (6:1), carrying the burdens of others (6:2), giving generously to those who teach in the church (6:6) and doing good to all (6:9). Sometimes sowing to the Spirit has been defined in terms of private, personal holiness, as if it were something done in a closet by oneself. But sowing to the Spirit in the context of Paul's teaching here involves building love relationships with others. Sowing to the Spirit cannot be done in isolation or separation from others. Carrying the burdens of others requires in-depth participation in their pain and sorrow. As we see in verse 9, sowing to the Spirit means doing good to others. If sowing to the sinful nature means selfish indulgence, then sowing to the Spirit means selfless service. The harvest of sowing to the Spirit is eternal life. The meaning of eternal life must be understood within the "already-not yet" structure of Paul's thought in this letter. From Paul's perspective, Christians have already been delivered from the present evil age (1:4) and are already in the new creation (6:15). But the battle between the Spirit and the sinful nature is not yet over (5:17). In Christ we already have new relationships with God and with one another: we now relate not as slaves but as children who call God Father (4:6-7); and we relate to one another not as people divided by racial, social and gender barriers but as people united in Christ (3:28). But since the battle between the Spirit and the sinful nature continues, we do not yet experience total harmony in these relationships. Those who continue to grow in these relationships by the power of the Spirit will ultimately experience the fullness of eternal life—perfect harmony in relationship with God and others.