Sacred theology is a practical habit that teaches how to worship God and reach eternal life
Book I. On the nature and constitution of sacred theology. Chapter 1. On the definition of theology.
Theology is a practical habit of the intellect, fully sealed by the mystical Holy Spirit from the divine disclosure in the Holy Scriptures, teaching a person on the Spirit's way — according to age, calling, and the measure of his own faith — the manner of worshipping God and of obtaining eternal life, unto the glory of God.
Scholion. First it is asked what the word theology properly signifies: whether in Holy Scripture one reads a God-speech or God-discourse — that is, the reason or speech of God by which we are instructed by God — or the reason, speech, or mental conception about God and divine things formed from the Scriptures by the power of the Holy Spirit. It is taken here in both senses.
For most weightily blessed Irenaeus says that no one can truly know God unless God himself teaches; from (John 6:45): It is written in the Prophets, And they shall all be taught by God. Whoever therefore has heard from the Father and has learned comes to me. For it is not left, says Hilary in book 7 On the Trinity, to human eloquence to speak of the things of God by other words than the speech of God. All other things are narrow, shut in, hindered, and obscure. If anyone wants to demonstrate this by other words than those by which it was spoken by God, either he himself does not understand, or he leaves it not to be understood by his readers. From book 1 On the Trinity: When the discourse is about the things of God, let us grant the knowledge of himself to God; let us serve his speech with pious reverence. For he is a fit witness for himself who is not known as to himself. Let the mystery of heaven, says Ambrose in book 5, letter 31, be taught me by God himself who made it, not by man who has not known himself. To whom should I rather trust concerning God than to God?
Yet lest some fanatic abuse Christ's saying in (John 6:45), here is worth considering the exposition which Urbanus Regius, a serious theologian of the past age, has in the body of doctrine to Julius on formulas for speaking carefully, under the ninth title. We, he says, do not rashly produce this place. For by the unskilled it is tossed about as an encomium of ignorance. And here they think they have a word of God by which all the liberal arts and even the studies of theology themselves may be exploded. Christ sufficiently explains this place in John 6: No one can come to me unless the Father who sent me draws him, and I will raise him up on the last day. And it is written in the prophets: And they shall all be taught by God. Everyone therefore who has heard from the Father and has learned comes to me. Here Christ speaks of that common doctrine necessary for all who are to be saved, by which we acknowledge Christ to be the Son of God made man for our salvation, and believe in him as our only Savior. By this doctrine certainly all the elect are illuminated; and those who lack it will be condemned. But there is also in the church another learning, which is called the gift of prophecy, with which gift not all Christians are endowed, but those who are set over churches for teaching, that they may expound the Holy Scriptures unto edification, exhortation, and consolation, of which mention is made in (1 Corinthians 14:1-5). This gift is not common to all believers — to tailors and cobblers and apostles alike. Those who lack it ought not to teach in the church, but reverently to hear those who teach, as the Apostle says: If there is no interpreter, let him keep silence in the church, and let him speak to himself and to God.
Indeed the word theology is not read expressly in the Scriptures except for its cognate in the title of the Apocalypse, where John the Evangelist is called Theologian in the strictest sense, as one who asserted the divinity of the Word both by the Gospel history and by his Apocalypse. Yet the term is frequented by the ancient fathers, by profane writers, by the schoolmen, and finally by more recent theologians. Nor is it necessary that a technical vocabulary exist in the Scriptures, because they do not propose the formulas of arts and disciplines, but the things to be believed unto salvation.
Latin
LIBER PRIMUS De S. S. Theologiae natura et constitutione. CAPUT PRIMUM. De Theologiae definitione. Theologia est habitus intellectus practicus, e patefactione divina sacris scripturis mystico Spiritu S. plene consignata, hominem in via Spiritus pro aetate, vocatione et mensura fidei suae, docens rationem colendi DEO et consequendi vitam aeternam, ad DEI gloriam. SCHOLION. Principio hic quaeritur, quid significet proprie vox THEOLOGIA, an in sacra Scriptura legatur Theoloquium, Deiloquium, id est rationem vel orationem DEI, qua a DEO instituimur; aut rationem, vel orationem, vel conceptum mentis de DEO rebusque divinis e scripturis virtute Spiritus sancti efformatum: quo utroque sensu hic accipitur. Nam gravissime B. Irenaeus: DEUM, inquit, vere agnoscere nemo potest, nisi DEO ipso docente; ex Joh. 6.45. Est scriptum in Prophetis, Et erunt omnes docti a DEO. Quisquis ergo audivit a Patre et didicit venit ad me. Non enim relictis est, ait Hilarius lib. 7. de Trin., hominum eloquiis de DEI rebus, aliis, praeterquam DEI sermo. Omnia reliqua et arcta et conclusa et impedita sunt et obscura. Si aliquis aliis verbis demonstrare hoc, quam quibus a DEO dictum est, volet: aut ipse non intelligit, aut legentibus non intelligendum relinquit. Ex lib. 1. de Trin.: Cum de rebus DEI sermo est, concedamus cognitionem sui DEO; dictioni ejus pia veneratione famulemur. Idoneus enim sibi testis est qui seipsum cognitus non est. Coeli mysterium, ait Ambrosius lib. 5. ep. 31., doceat me Deus ipse qui condidit, non homo qui seipsum ignoravit. Cui magis de DEO, quam DEO credam? Ne tamen quis fanaticus dicto Christi Joh. 6.45. abutatur, hic digna considerata est ejus expositio, quam habet Urbanus Regius, praeteriti seculi gravis Theologus, in corpore doctrinae Julio de formulis caute loquendi sub titulo nono. Nos, inquiens, temere hunc locum produco. Nam ab imperitis jactatur tanquam encomium IMPERITIAE. Et hic putant se verbum DEI aet habere, quo OMNES BONAE ARTES et ipsa denique Theologiae studia explodantur. Christus satis explicat hunc locum Joh. 6. Nemo potest, inquit, venire ad me nisi Pater, qui misit me, traxerit eum, et ego resuscitabo eum in novissimo die. Et scriptum in prophetis: Et erunt omnes docti a DEO. Omnis ergo qui audivit a patre, et didicit, venit ad me. Hic Christus de COMMUNI illa et OMNIBUS SALVANDIS NECESSARIA doctrina loquitur; qua Christum agnoscimus esse Filium DEI propter nostram salutem hominem factum, et in eum, ut nostrum unicum Salvatorem, credimus. Hac doctrina illuminantur certe omnes electi: et qui ea carent, condemnabuntur: sed est etiam in ecclesia ALIA ERUDITIO, quae vocatur DONUM PROPHETIAE, quo dono donantur non omnes Christiani, sed qui Ecclesiis docendis praeficiuntur ut Scripturas sanctas exponant, ad aedificationem, exhortationem et consolationem, cujus mentio fit 1. Cor. 14. Hoc donum NON EST OMNIBUS CREDENTIBUS, SARTORIBUS et SUTORIBUS et Apostolis commune: quo qui carent, non debent docere in Ecclesia, sed docentes reverenter audire, ut Apostolus ait: Qui non est interpres, taceat in Ecclesia, ceterum sibi ipsi loquatur et Deo. Haec ibidem. In scripturis quidem disertim non legitur vox Theologia praeter illius conjugatum in inscriptione Apocalypsis, ubi Johannes Euangelista Theologus dicitur; strictissimo significatu; qui asseruit divinitatem Logou tum historia Euangelica, tum Apocalypsi sua: frequentatur tamen tum a priscis patribus, tum a profanis scriptoribus, tum a scholasticis, tum denique a recentioribus Theologis. Neque opus est, ut vocabulum technicum in scripturis exstet; quia hae non formulas artium ac disciplinarum, sed res credendas ad salutem proponunt.