De Deo uno

1. “We firmly believe and simply confess that there is one only true God, eternal, immense and immutable, incomprehensible, omnipotent and ineffable, Father and Son and Holy Spirit: three persons indeed, but one wholly simple essence, substance, or nature” (Conc. Lat. IV; Denz 428). Therefore the true God is one and triune. Hence this treatise takes as its subject both the unity of the nature and the trinity of the persons in God himself.

PETER LOMBARD, the Master of the Sentences, treats both the one and triune God in the first book of the Sentences; all the scholastics who wrote commentaries on the books of the Sentences followed him in this. ST. THOMAS does likewise in his commentary; later, in the Summa Theologica, he treats separately 1) what pertains to the divine essence (q. 2-26), and 2) what pertains to the distinction of the persons (q. 27-43). The scholastics who composed commentaries on the Summa initially retained this division, and it was subsequently adopted universally. It is now customary to present two treatises “On God himself”: one “On the one God,” the other “On the triune God.” The present treatise is on the one God.

2. What pertains to the distinction of the divine persons can be known only through positive revelation. Many things, however, concerning God insofar as he is one are not in themselves inaccessible to human reason; hence they can in some way be known by reason alone. This is why there is a philosophical treatise, natural theology, which itself may also be called “A Treatise on the One God.” Nevertheless, although that philosophical treatise resembles the theological treatise in part with respect to its subject matter, the two must in no way be confused. Their sources are entirely different: in the philosophical treatise, reason, by reasoning and drawing conclusions from the natural manifestation of God contained in the work of creation, ascends to knowledge of God’s existence and attributes; but the source of our theological treatise “On the One God” is positive revelation, to be embraced in faith on the authority of God himself, who reveals. Therefore, in our theological treatise, the question is not so much what reason teaches about the one God, but what God himself has testified about himself in revelation.

Accordingly, the place occupied by reason in the present treatise is entirely different from that which it occupies in “natural theology,” and also different from that which it occupies, at least in part, in fundamental theology, namely, demonstrating the foundations of faith (Conc. Vat., s. 3 c. 4; Denz 1799). In dogmatic theology, the task of reason is to explain, uphold, and defend revealed truths (Pius IX; Denz 1634, 1635); right reason, illumined by the light of faith, cultivates the science of divine things (Conc. Vatic. s. 3 c. 4; Denz 1799).

3. Because this dogmatic treatise resembles the philosophical treatise just mentioned, care must be taken that the treatise on the one God truly be and remain theological. The method of proceeding and proving, even in questions that are the subject of “natural theology,” must be theological above all, proceeding from the principles of faith, and not principally from “reason.” For this purpose, what GREGORY IX wrote to the theologians of Paris in 1228 may usefully be considered (Denz 442 s.); it will suffice to cite the following:

“Far be it henceforth that the most beautiful of women (that is, theology), her eyes smeared with antimony, should be painted with counterfeit colors by presumptuous men; and that she, who comes forth splendid as a queen, clothed by her bridegroom in many-colored garments¹ and adorned with jewels², should be dressed in a filthy garment sewn from philosophers’ half-girdles. Far be it that ugly oxen, wasted by emaciation and showing no sign of satiety, should devour the beautiful ones³ and consume the fat ones. Therefore, lest such a rash and perverse doctrine spread like a cancer⁴, infect many, and compel Rachel to weep for her lost children⁵, by the authority of this letter we command and strictly enjoin you to renounce utterly the aforesaid madness and to teach theological purity without the leaven of worldly learning, not adulterating the word of God⁶ with the fictions of philosophers, lest you seem to wish to plant a grove beside the altar of God contrary to the Lord’s command, and to leaven the sacrifice of doctrine with a mixture of honey, when it ought to be offered in the unleavened bread of sincerity and truth⁷” (GRABMANN, I divieti ecclesiastici di Aristotele sotto Innocenzo III e Gregorio IX. Miscell. Hist. Pontif. nr. 7. Romae 1941, cap. 2). Cf. Denz 1642; 1656; 1666 s.; 1670 ss.; 1681; 1708.

4. The functions that belong to reason in other dogmatic treatises are also to be assigned to it in our treatise: namely, to explain and defend revealed truths, to make clear the connections and relations among them, and the like. Since these matters have already been treated at length for the most part in the philosophical treatise, which is presupposed in its entirety, it will be enough, to avoid repetition, merely to indicate them briefly in their proper places and refer the reader to the philosophical treatise for further explanation.

5. In dogmatic theology there is scarcely any proper place for the question whether God exists. For dogmatic theology must proceed from the principles of faith and therefore presupposes positive divine revelation and, by that very fact, God’s existence. It is right, however, to ask what God has revealed about his knowability; we shall consider this question first, since it is especially important in our own times. Next we ask what revelation teaches about the divine perfections; third, what it teaches about God’s knowledge and will; and finally, what it teaches about predestination and reprobation.