The Greek word “logos” signifies both Word and Reason. But in this passage it is better to interpret it Word; as referring not only to the Father, but to the creation of things by the operative power of the Word; whereas Reason, though it produce nothing, is still rightly called Reason.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: lib. lxxxiii. Quæst. q. 63
