Full Idea
The passions may incite us to something against reason, and so we need a curb, which we name 'temperance'.
Gist of Idea
Temperance prevents our passions from acting against reason
Source
Thomas Aquinas (Summa Theologicae [1265], Ia 2ae Q61 a.3), quoted by Philippa Foot - Virtues and Vices II
Book Reference
Foot,Philippa: 'Virtues and Vices' [Blackwell 1981], p.9
A Reaction
I am increasingly unclear what 'reason' means in contexts like these. It seems to mean no more than the awareness of greater goods than the indulgence of passion. Without that awareness, high intelligence couldn't produce temperance.