The Transcendental Argument (TAG). From WikiPedia: The Transcendental Argument is an argument for the existence of God that attempts to show that logic, science, ethics (and generally every fact of human experience and knowledge) are not meaningful apart from a preconditioning belief in the existence of God.
Eg. Knowledge cannot be obtained absolutely unless the source of that knowledge is itself an absolute source (read: being/God). Ergo, either you sub-consciously believe in an absolute being that upholds and makes absolute the laws of the universe/morality OR you do not and CAN NOT know anything for certain.
So what? Many non-theists when they are backed against the wall will admit that they know nothing with 100% certainty.
Some claim that TAG employs Circular reasoning. However, there are counter-counter-arguments to this.
Others claim that TAG is a variation of the Ontological argument.