That’s easy enough- by the size of his library. Sadly, among Reformed Christians this sometimes seems to be our standard. Were we to narrow our library down a smidge to the Word of God we would find there a far more clear answer- the fruit of the Spirit.
Fruit, as a general rule, does not pop up overnight. One does not plant a seed today and come back tomorrow looking for the harvest. The fruit of the Spirit is much the same. It is not that one must wait five or ten years after ones conversion before one can manifest love, joy or peace. The point is instead that these blessings will flourish and ripen over time as they are cultivated by the Spirit.
One of the challenges we face is faux fruit, wax versions created by the Great Deceiver to deceive us. Love, for instance, in our peculiar time, is essentially equated in the public mind with mere permissiveness. The mature Christian doesn’t smile blandly in the face of grievous sin. Genuine love mourns for the destructive power of sin. Genuine love enters into the lives of others, mourning with those who mourn.
Joy, as well, should not be understood as mere happiness. It is instead something far more august, more unshakable, more rich. Do you see in the Christian joy even in the context of hardship? Is this person rejoicing in the grace of God, in the glory of Christ, even when health is elusive, or even in the loss of a loved one? Here joy intersects with peace. The mature Christian doesn’t merely believe in the sovereignty of God in the abstract, winning arguments over predestination. The mature Christian instead rests in the knowledge that God Himself brings all things to pass. President Obama to the mature Christian, isn’t the cause of the sky falling. He is instead what God has given us for our good and His glory. Peace rests.
We can recognize the mature Christian in how he reacts to we who are immature. Patience means not growing frustrated with the rest of us, and our weaknesses. The mature Christian remembers his own journey, and again rests in confidence that God is on His throne. This will show itself in turn as kindness. The mature Christian looks for opportunities to encourage and help others rather than to criticize and attack others. Which in turn is an expression of gentleness. The mature Christian knows that his strength is in the Lord, and thus has no need to throw his weight around. Self-control then isn’t merely avoiding fatty foods. It isn’t control over impulse buying. It is mastery of ones emotions. It is decision making grounded in the Word.
Which brings us to faithfulness. Faithfulness isn’t the first on the list, nor the last. It does, however, in my judgment, neatly subsume them all. The mature Christian is the person whose passion is to submit to all that the Bible teaches. He is faithful to the Lordship of Christ, focused on his calling to become more like Him. His pursuit isn’t human accolades, professional success. Instead he labors daily to win this great prize, to hear Jesus declare, “Well done, thou good and faithful servant. Enter into your reward.”
The mature Christian, however, more than anything else, knows himself. He knows his failures and his weaknesses. I would suggest then that in the end the clearest mark of the mature Christian is the mark of the Christian- repentance. We are never closer to the mark then when we are most conscious of how far off the mark we are, when we beat our breast and cry out, “Lord, be merciful to me, a sinner.”