SAINT THOMAS AQUINAS. BtVS Intertext/Allusion.
In "Beer Bad" we find the following dialogue in a campus pub (from the transcript at BuffyWorld.com, slightly corrected):
Buffy: My mother always said that beer was evil.
Guy #1: Evil. Good. These are moral absolutes that predate the absolution of malt and fine hops. You see, wait where was I?
Buffy: I'm really not sure:
Guy#4: Well, Thomas Aquinas and . . . (all the other guys stop him saying “NO”)
Guy #2: There will be no Thomas Aquinas at this table.
Guy#3: Keep your theology of providence to yourself frat boy.
Guy#4: I was just drawing a parallel between.
Guy#1: Beer. Had the earliest morality developed under the influence of beer there would be no good or evil. There would just be kinda nice and pretty cool. Everything would be different.
Buffy: You guys really like to hear yourselves speak don't ya.
Aquinas (1225-74) was a medieval Italian theologian, one of the intellectual fathers of Catholicisim and the author of Summa Theologica (1265-72). Go here to read the Catholic Encyclopedia's account of his life and work.