Problema de veritatis et pacis tē syzygia

as the golden foundation and source of all duties and virtues, I prefer to understand the Gospel, which is the knowledge of the truth that is according to godliness.

The same TRUTH, κατ' ἀφαίρεσιν τοῦ ἐναντίου by the exclusion of the opposite, is doctrine entirely alien to ἑτεροδιδασκαλία heterodoxy/strange teaching, or diverse doctrine, which embraces foolish and unlearned questions, λογομαχίας word-battles, and myths: and begets perverse exercises. 1 Timothy 6:4-5 and 2 Timothy 2:23 and chapter 4:4.

The same, κατὰ θέσιν according to the position/thesis, is the analogy of faith. Romans 12:6. Therefore, Faith is called by περίφρασιν circumlocution, the knowledge of the truth which is according to godliness. 1 Timothy 2:4, Titus 1:1. And κατὰ συνωνυμίαν by synonymy, they are called both the faithful and those who know the truth. 1 Timothy 4:3. Finally, καθ' ἀντίθεσιν by antithesis, those who resist the truth are opposed to the faithful; they are men of corrupt mind and reprobate concerning the faith. 2 Timothy 3:8.

But omitting these descriptions, let us append the definition of the thing, sought from the writings of the same Apostle.

TRUTH is that sound doctrine of God, according to godliness, concerning Jesus who is Christ and Lord, and therefore it is the power of God unto salvation to everyone who believes.

The Διόρθωσις correction/emendation of this definition shall be this:
1. The αἴτιον κύριον principal cause of this Gospel, or truth, is GOD. Romans 15:16.
2. The genus is Doctrine. 1 Timothy 6:3. And when its heard word is mixed with faith, then truly the type of doctrine is imprinted, so that obedience of faith may be rendered from the heart. Hebrews 4:2, Romans 6:17 and 1:5.
3. The differentia is Sound. The truth is sound, both with respect to itself, because it is sincere, eternal, and alien to all contagion of falsehood and corruption: and because, just as Opobalsamum balsam of balm instilled into a wound heals it: so the truth of the Gospel written upon a contrite heart heals it most effectively. Isaiah 57:15, 18 and 61:1.