one's ruling passion
First guess a man's ruling passion, appeal to it by a word, set it in motion by temptation, and you will infallibly give checkmate to his freedom of will.
The ruling passion of them miser is the love of money.
First guess a man's ruling passion, appeal to it by a word, set it in motion by temptation, and you will infallibly give chechmate to his freedom of will.
Even my love of literary fame, my ruling passion, never soured my temper.
Their ruling passion is that of carnal love.