Truer words never spoken. To 'know' removes all doubt. Either you know or you don't. There is no in-between concerning truth. The quest for knowledge is the oldest quest in human history. The gauge of humanity's progression falls upon acknowledgment of this quest within the scope of one’s very own life. Those who do not wish to know settle for belief. With knowledge comes the dispellment of belief, and the need for it.
How do you know? You know when you know that you know.