Scotus Academicus, Tomus primus: De Deo in se subsistente

We have already said clearly enough in the prelude to theology that the books of the Sentences have as their author and parent Peter Lombard, Bishop of Paris; for although that most wise prelate seems in these books to have gathered not so much his own opinion as the opinion of the holy Fathers, yet he justly claims these illustrious offspring of his genius as properly his own, and glories in the name of their author. For, as the Seraphic Bonaventure noted, q. 4. of the Prologue:

There is a fourfold way of making a book. For one person writes another's material, adding or changing nothing, and he is called merely a writer; one person writes another's material with additions, but nothing of his own, and he is called a compiler; one person writes both another's material and his own, but the other's as principal and his own as annexed for clarity, and he is called a commentator; one person writes both another's material and his own, but his own as principal and the other's as annexed for confirmation, and such a one ought to be called an author.

Such was the Master, since he sets down his own opinions and confirms them with the opinions of the Fathers; whence he truly ought to be called the author of this book.

Moreover, this book, the sanctuary of all divine wisdom, the same Seraphic Doctor not undeservedly likens to that wondrous fountain which God had placed in the midst of the earthly Paradise, so that by its perennial overflowing it might water and fertilize the whole earth; for, to pass over many things which would wonderfully commend the comparison of the two, it is pleasing to relate this one thing: that just as that paradisiacal fountain spread out into four heads, or rivers, which, winding far and wide, watered and refreshed the orb of the earth, so theology, that mystical fountain of divine wisdom, is distributed into the four books of the Sentences as into so many rivers of light, that it may steep the Christian world in heavenly light and irradiate it on every side with divine splendor.

For all theology is taken up and occupied with this: that it may show forth and exhibit God, either as subsisting, operating, and producing in the order of divinity; or, according to the order of nature, as producing, governing, and ordering creatures; or, according to the supernatural order of grace, as devising and effecting the salvation of men in the assumed humanity; or finally, as leading them to the order of glory through the sacraments, as through necessary and efficacious means.

The first book of the Sentences, therefore, is set before us to be completed in three treatises: in the first of these we shall contemplate God subsisting in Himself, and so His essence, existence, and excellences; in the second, we shall behold God operating through intellect and will, both with respect to Himself and in order toward creatures, whom He knows by His knowledge, governs by His providence, and orders by predestination to a supernatural end; finally, in the third, we shall undertake to explain God producing within Himself, and the adorable mystery of the Trinity.