Faith must be professed and defended
Augustine opens the treatise by explaining why the creed must be held in the heart, confessed with the mouth, and defended against heretics.
Since it is written, and confirmed by the most robust authority of apostolic teaching, that the righteous person lives by faith, and since this faith demands from us the service of both heart and tongue—for the apostle says, "With the heart one believes and is justified, and with the mouth one confesses and is saved" (Romans 10:10)—we must be mindful of both righteousness and salvation. For we are destined to reign in everlasting righteousness, and we cannot be saved from this present wicked age unless we also strive for the salvation of our neighbors and profess with our mouth the faith we carry in our heart. We must take pious and careful watch that this faith cannot be violated in us in any part by the deceitful cunning of heretics.
Now the catholic faith is known to the faithful in the creed and committed to memory, in as brief a form of words as so great a matter allows. Its purpose is that for beginners and infants—those who have been reborn in Christ but are not yet strengthened by the most diligent and spiritual study and knowledge of the divine Scriptures—what they are to believe should be set down in few words, while for those advancing and rising to divine teaching with the firm foundation of humility and love, it would need to be expounded in many words. Under those very few words set down in the creed, many heretics have tried to hide their poisons. Divine mercy has resisted them, and still resists them, through spiritual men who have merited not only to receive and believe the catholic faith in those words, but also to understand and know it by the Lord's revelation. For it is written, "Unless you believe, you will not understand" (Isaiah 7:9).
But an exposition of the faith serves to fortify the creed—not so that it should be handed over in place of the creed to those who are attaining God's grace, to be memorized and recited, but so that the things held in the creed may be guarded against the snares of heretics by catholic authority and a more fortified defense.
Latin
Quoniam scriptum est et apostolicae disciplinae robustissima auctoritate firmatum. quia iustus ex fide uiuit, eaque fides officium a nobis exigit et cordis et linguae — ait enim apostolus: corde creditur ad iustitiam, ore autem confessio fit ad salutem — oportet nos esse et iustitiae memores et salutis, quandoquidem in sempiterna iustitia regnaturi a praesenti saeculo maligno salui fieri non possumus, nisi et nos ad salutem proximorum nitentes etiam ore profiteamur fidem, quam corde gestamus: quae fides ne fraudulentis calliditatibus haereticorum possit in nobis aliqua ex parte uiolari, pia cautaque uigilantia prouidendum est. est autem catholica fides in symbolo nota fidelibus memoriaeque mandata quanta res passa est breuitate sermonis: ut incipientibus atque lactantibus eis, qui in Christo renati sunt, nondum scripturarum diuinarum diligentissima et spiritali tractatione atque cognitione roboratis paucis uerbis credendum constitueretur, quod multis uerbis exponendum esset proficientibus et ad diuinam doctrinam certa humilitatis atque caritatis firmitate surgentibus. sub ipsis ergo uerbis paucis in symbolo constitutis plerique haeretici uenena sua occultare conati sunt: quibus restitit et resistit diuina misericordia per spiritales uiros, qui catholicam fidem non tantum in illis uerbis accipere et credere, sed etiam domino reuelante intellegere atque cognoscere meruerunt. scriptum est enim: nisi credideritis, non intellegetis. sed tractatio fidei ad muniendum symbolum ualet: non ut ipsa pro symbolo gratiam dei consequentibus memoriae mandanda et reddenda tradatur, sed ut illa, quae in symbolo retinentur, contra haereticorum insidias auctoritate catholica et munitiore defensione custodiat.