Aggression (generally speaking)
The quote is loosely paraphrased from Rounders, which is just a movie, but Doyle wrote about it before I was born.
"If it's good enough for a call, you need to be in there raising."
Generally speaking, I'm in agreement with this. Even though it appears to suggest that when faced with a bet if you're going to call anyway you should raise. That IS NOT IT AT ALL. It is saying, if you *would* call a bet, but you're either first to act or it has been checked to you THEN show some moxie.
The only caveat I would toss on there is when you feel your opponent has pretty much nothing, your bet would take it down, which is fine, but you consider trying to siphon off a few more chips by giving him a chance to bluff at it.
Happy to hear counter-points!