From R. C. Sproul, The Mystery of the Holy Spirit [pp. 165-7.]:

Here [in Galatians 5:22-25] the Apostle exhibits the model of authentic righteousness. The fruit is designated as the fruit of the Spirit. Fruit is something that is produced in us. It is not of ourselves. In ourselves we are only flesh. The flesh produces nothing but more flesh. The deeds of the flesh are the fruit of the flesh. The flesh profits nothing. Martin Luther declared that “nothing” is not a “little something.”

Like begets like. The product comes from the producer. The progeny recapitulates the ontogeny. Only the Holy Spirit can conceive and bear the fruit of the Spirit. We can be skilled preachers without the Spirit. We can be theological geniuses after the flesh. We can be silver-tongued orators apart from grace. But the only source of the fruit of the Spirit is the work of the Holy Spirit within us.

It is no accident that the fruit of the Spirit is not elevated in our ranks as the highest test of righteousness. There abides so much flesh in us that we prefer another standard. The fruit test is too high; we cannot attain it. So within our Christian subcultures we prefer to elevate some lesser test by which we can measure ourselves with more success. We can compete with each other with greater facility if we mix some flesh together with Spirit.

How hard it is for us to be measured by our love! And please don’t evaluate me by the standard of gentleness. I’m far too impatient to deserve patience as my standard of growth. It is easier for me to preach than to forbear It is easier for me to write a book about peace than to practice peace.

The fruit of the Spirit includes a list of virtues that on the surface appear to be commonplace. John Calvin spoke of virtues that unregenerate pagans are capable of displaying to some degree. He described the “civil righteousness” achieved by natural man. By the common grace of God, fallen creatures exhibit an external form of righteousness.

External righteousness is that which outwardly corresponds to the law of God but lacks the motivation from a heart disposed toward the love of God. Unbelievers can love by a natural affection. Unbelieving husbands have a natural affection for their wives. Unbelieving mothers have a natural affection for their children. Secular music extols the virtue of love.

So also the other virtues mentioned as the fruit of the Spirit may be manifest among the ungodly. There were moments when Adolph Hitler was kind. Stalin had momentary displays of gentleness. The Pharaoh of Moses’ Egypt at times lapsed into patience. In our own day the Mormons are noted for being temperate.

Herein is the problem. If unbelievers can exhibit the virtues mentioned in the fruit of the Spirit, how can we know if the presence of these virtues in any way indicates the presence of the Spirit in our lives? Not a single fruit of the Spirit, externally exhibited, is a proof of regeneration.

Perhaps it is because of the facility of confusion between “civil righteousness” and the fruit of the Spirit that Christians tend to look elsewhere for indicators of true godliness. But the Bible would not have us yield to this temptation. The Spirit yields authentic fruit. It is His work that we are to cultivate in our lives. (Since even unbelievers can be kind, gentle, peaceful, etc., Christians often focus on such concerns as eloquent preaching, writing, etc. Being good–showing the fruit of the Spirit–in an unobtrusive way is less dramatic but possibly more godly than being an excellent preacher, religious author, gospel singer, etc.)

We must learn to discern the difference between civil righteousness and the fruit of the Spirit. The difference is more than one of degree. It is a difference of kind as well.