I dusted off again recently Herman Witsius’s excellent essay “On the Character of a True Theologian.” As you can tell from the title, his emphasis is that a theologian is first a person of character, who loves God and believes what he teaches. Here’s one of the best paragraphs:
By a theologian, I mean one who, imbued with a substantial knowledge of divine things derived form the teaching of God himself, declares and extols, not in words only, but by the whole course of his life, the wonderful excelencies of God and thus lives entirely for his glory.
Such were in former days the holy patriarchs, such the divinely inspired prophets, such the apostolic teachers of the whole world, such some of those whom we denominate fathers, the widely resplendent luminaries of the primitive church. The knowledge of these men did not lie in the wiredrawn subtleties of curious questions, but in the devout contemplation of God and his Christ.
Their plain and chaste mode of teaching did not soothe itching ears but, impressing upon the mind an exact representation of sacred things, inflamed the soul with their love, while their praiseworthy innocence of behavior, in harmony with their profession and unimpeached by their enemies, supported their teaching by an evidence that was irresistible, and formed a clear proof of their having familiar intercourse with the most holy God.
So that is the character of a true theologian: he seeks knowledge not for its own sake, but in communion with God, and lives what he teaches.
But what is the doctrine of a true theologian? Luther answers this, and Witsius would agree:
Anyone who can judge rightly between the law and the Gospel should thank God and know that he is a true theologian.
In other words, a true theologian knows that we are justified by faith alone in Christ alone (the gospel) and not works (the law). This is what Luther rightly calls “the sum” and “chief article of all Christian doctrine.” “This is the beginning of health and salvation. By this means we are delivered from sin, justified, and made inheritors of everlasting life, not because of what we have done to deserve it, but through our faith, by which we lay hold of Christ. . . . Faith takes hold of Christ as a ring does a precious stone. Whoever has this confidence in Christ will be accounted righteous by God.”
At the foundation of the character of a true theologian is a doctrine, a truth, namely the gospel. This is what then enables a theologian to truly seek God, develop the character God requires, and live out the truth of the Scriptures.