Faith and skepticism.

In all matters of life, skepticism will save you from getting trapped by scams, cheats, liars, frauds, pyramid schemes, cults, and anything else that might trick you.

And faith is your greatest enemy. Faith is the doom upon your own mind that you yourself place there. Faith is a fully loaded shotgun aimed at your delicate brain, ready to splatter it into little red bits.

Faith tricks you into thinking a thing is true, without that thing actually being true. Faith is the reason people can be tricked so easily. Fool a person into having "faith" in an untrue idea, and that person is your slave forever, bound to spread the memetic virus.