Most people are familiar with the Summa Theologica, which is lovely, but was meant as an introductory text for theology students. More importantly for us, Summa Contra Gentiles was written as a guide for folks lacking the vocabulary of classical metaphysics and theology, as we’ll see.
The translation is from the English Dominican Fathers, and you can go there for the complete original. We won’t need the whole book, so any expurgated text will be noted by ellipsis or notes. I’ll break text up in the modern way for easy screen reading.
I’ll keep the original bracketed footnotes, e.g. “”, for references, and he helpfully numbered his thoughts within a chapter, e.g. “(3)“. I’ll add my footnotes in lowercase Latin, e.g. “iv“. Some chapters will need many notes, others scarcely any. I’ll also freely translate the titles, but always link back to the original.
I am not the best man to do this, in the sense that many others know orders of magnitude more than I, but since knowledge of classical metaphysics is so lacking yet so necessary, anything I can offer will be at least somewhat helpful. Plus, I am convinced that after you go through even a few chapters, you’ll be amazed if not convinced.
Book 1 has about 100 chapters, so that’s two years averaging one a week. Who’s in a rush? So without further ado, Chapter 1, which is a plea that one should not lead an unexamined life and that Truth is always our goal. Who could disagree with that? Nobody, that’s who, thus there are few notes.
My mouth shall meditate truth, and my lips shall hate wickedness.–PROV. viii. 7.
(1) The general use which, in the Philosopher’si opinion, should be followed in naming things, has resulted in those men being called wise who direct things themselves and govern them well…
Now the rule of all things directed to the end of government and order must needs be taken from their end: for then is a thing best disposed when it is fittingly directed to its end, since the end of everything is its good…
The same may be observed in the art of sailing in relation to the art of ship-building, and in the military art in relation to the equestrian art and all warlike appliances. These arts which govern others are called master-arts (architectonicæ), that is principal arts, for which reason their craftsmen, who are called master-craftsmen (architectores), are awarded the name of wise men.
Since, however, these same craftsmen, through being occupied with the ends of certain singular things, do not attain to the universal end of all things, they are called wise about this or that, in which sense it is said (1 Cor. iii. 10): As a wise architect, I have laid the foundation; whereas the name of being wise simply is reserved to him alone whose consideration is about the end of the universe, which end is also the beginning of the universe: wherefore, according to the Philosopher, it belongs to the wise man to consider the highest causes.
(2) Now the last end of each thing is that which is intended by the first author or mover of that thing: and the first author and mover of the universe is an intellect, as we shall prove further on. Consequently the last end of the universe must be the good of the intellect: and this is truth. Therefore truth must be the last end of the whole universe; and the consideration thereof must be the chief occupation of wisdom.
…Moreover the Philosopher defines the First Philosophy as being the knowledge of truth, not of any truth, but of that truth which is the source of all truth, of that, namely, which relates to the first principle of being of all things; wherefore its truth is the principle of all truth, since the disposition of things is the same in truth as in being.
(3) Now it belongs to the same thing to pursue one contrary and to remove the other: thus medicine which effects health, removes sickness. Hence, just as it belongs to a wise man to meditate and disseminate truth, especially about the first principle, so does it belong to him to refute contrary falsehood.
(4) Wherefore the twofold office of the wise man is fittingly declared from the mouth of Wisdom, in the words above quoted; namely, to meditate and publish the divine truth, which antonomasticallyii is the truth, as signified by the words, My mouth shall meditate truth; and to refute the error contrary to truth, as signified by the words, and my lips shall hate wickedness, by which is denoted falsehood opposed to divine truth, which falsehood is contrary to religion that is also called godliness, wherefore the falsehood that is contrary thereto receives the name of ungodliness.
iThe Philosopher is always, and of course, Aristotle.
iiThe substitution of a title or epithet for a proper name, such as “Statistician to the Stars!” for William M. Briggs.
 1 Metaph. i. 12; ii. 7.
 Ch. xliv.; Bk. II., ch. xxiv.
 Ia Metaph. i. 4, 5.