Those who claim for themselves to judge the truth are bound to possess a criterion of truth. This criterion, then, either is without a judge’s approval or has been approved. But if it is without approval, whence comes it that it is truthworthy? For no matter of dispute is to be trusted without judging. And, if it has been approved, that which approves it, in turn, either has been approved or has not been approved, and so on ad infinitum – Sextus Empiricus.
He raised concerns which applied to all types of knowledge and advocates simply giving up belief: that is, suspending judgment about whether or not anything is knowable. Only by suspending judgment can we attain a state of peaceful enlightenment (Ataraxia).
Taraxia means something like mess. When you put an ‘a’ before a word in the Greek language it means ‘the opposite’ of what the original word means. Ataraxia signifies the balanced state of robust tranquility that derives from eschewing faith in an afterlife, not fearing the gods because they are distant and not concerned with us, avoiding politics and vexatious people, surrounding oneself with trustworthy and affectionate friends and, most importantly, being an affectionate, virtuous person, worthy of trust.
Enlightened individuals can escape periodically from their own hungers and passions and look down with compassion on poor humanity, including themselves, who are on average ignorant, unhappy, and yearning for something better than what they see around them. Personal responsibility then consists of speaking and living personal truth.
Skepticism goes back at least as far as Pyrrho of Elis. Pyrrho found peace by admitting to ignorance and seeming to abandon the criterion by which knowledge is gained. Pyrrho’s ignorance was not the ignorance of children or farm animals: it was a knowledgeable ignorance, arrived at through the application of logical reasoning and exposition of its inadequacy.