Proof of the Truth-criteria: everything I clearly and distinctly perceive is true. 1.) I lack any faculty whereby to discover anything I clearly and distinctly perceive to be mistaken. 2.) God would be a deceiver if, lacking such a faculty, my nautre was in fact so defective that I tended inexorably to error and illusion. 3.) By the conclusion of the proof that God is not a deceiver, it follows that it iis impossible that I am by nature prone to error (i.e. the metaphysical doubt grounded on the malicious demon hypothesis is refuted). 4.) Since the only ground I had for doubting things I clearly and distinctly perceive (i.e. intuitively and demonstratively apprehended propositions of logic, mathematics, and metaphysics) is now removed, it follows that everything I clearly and distinctly perceive is true.