On Doubt
We must ask if this "principle of universal doubt" is itself certain, or is it open to doubt as well? If it is known with certainty, at least one thing is beyond doubt, which makes the principle false. If, however, the principle is open to doubt -- i.e. , if it is not certain -- then on what grounds can the skeptic claim greater plausibility for his theory than any other other? --George H. Smith, Atheism: The Case Against God , 1974