The main principle of Pyrrho*s thought is expressed by the word acatalepsia, which connotes the ability to withhold assent from doctrines regarding the truth ofthings in their own nature; against every statement its contradiction may be advanced with equal justification. Secondly, it is necessary in view of this fact to preserve an attitude of intellectual suspense, or, as Timon expressed it, no assertion can be known to be better than another. Thirdly, Pyrrho applied these results to life in general, concluding that, since nothing can be known, the only proper attitude is ataraxia, "freedom from worry". ("By suspending judgment, by confining oneself to phenomena or objects as they appear, and by asserting nothing definite as to how they really are, one can escape the perplexities of life and attain an imperturbable peace of mind.")

The proper course of the sage, said Pyrrho, is to ask himself three questions. Firstly we must ask what things are and how they are constituted. Secondly, we ask how we are related to these things. Thirdly, we ask what ought to be our attitude towards them. Pyrrho*s answer was that things are indistinguishable, unmeasurable, undecidable, and no more this than that, or both this and that and neither this nor that. He concluded that human senses neither transmit truths nor lie.[2] Humanity cannot know the inner substance of things, only how things appear.
The impossibility of knowledge, even in regard to our own ignorance or doubt, should induce the wise person to withdraw into themselves, avoiding the stress and emotion which belong to the contest of vain imaginings. This theory of the impossibility of knowledge is the first and the most thorough exposition ofnoncognitivism in the history of Western thought.[citation needed] Its ethical implications may be compared with the ideal tranquility of the Stoics and theEpicureans.