Not only can water float a boat, it can sink it also.

Not only can water float a boat, it can sink it also. — The moral of this proverb, or a meaning could be There are opposite aspects of any tool or power.This concept is related to yin-yang (it can be used under such conditions as: the multitude can support the goverment or overthrow the goverment). (This is a rough translation from a Chinese proverb)