Find out each Man’s Thumbscrew. It is the art of setting their wills in action. It needs more skill than resolution. You must know where to get at any one. Every volition has a special motive which varies according to taste. All men are idolaters, some of fame, others of self-interest, most of pleasure. Skill consists in knowing these idols in order to bring them into play. Knowing any man’s mainspring of motive you have as it were the key to his will. Have resort to primary motors, which are not always the highest but more often the lowest part of his nature: there are more dispositions badly organised than well. 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 Art of Worldly Wisdom, Baltasar Gracian

Everyone has weaknesses. You should know what these are, and you should know which weaknesses you have yourself. Man is a victim of their his impulses – that is, Man suspends higher principles for the service of basic pleasures. Man is greedy and weak, and willing to exploit others for their fix.

When you are aware of what makes people tick, then you can control their actions. What they presume to be free will will be merely a pattern of behavior that you have set in motion, either with a phrase or a question. The people that know your thumbscrew the most are the people that are closest to you.

Notice when you are being manipulated by understanding your vulnerabilities. The most susceptible to manipulation is the person who affirms they have no weaknesses. They set the largest trap for themselves – all that is left for their enemy to do, is to tap gently on potential problem areas, and notice when the ferocity of  denial reaches its peak  – that is when the victim finally reveals his hand.

If you have reason to suspect that a person is telling you a lie, look as though you believed every word he said. This will give him courage to go on; he will become more vehement in his assertions, and in the end betray himself. Again, if you perceive that a person is trying to conceal something from you, but with only partial success, look as though you did not believe him. The opposition on your part will provoke him into leading out his reserve of truth and bringing the whole force of it to bear upon your incredulity.

– Arthur Schopenhauer