I have spoken already of the Summa Theologica, and in fact, it is the primary source and purpose of this blog. St. Thomas, of course, wrote prolifically, and all of his works are worth study and contemplation (a task I am far from completing). At this point, I am of the opinion that, although the Summa Theologica is “written for the instruction of beginners,” that in all actuality, the Summa Contra Gentiles, written earlier and actually complete (the Summa Theologica was never completed, as St. Thomas, in deep contemplation of God, realized “all he had written was as straw” compared to the beatific vision and thus refused to take up the pen again), is easier to read, for it is written in a straight forward style (without the objections and replies of the scholastic format) and thus for many would make a better introduction to the systematic thought of St. Thomas.
Written as four books, it is divided into two parts:
- That knowledge of God which can be reached by human reason alone
- That which can only be known by God’s revelation of Himself
It is available online for free here.