Mario Dal Pra’s survey of ancient skepticism from the initial phase of "trascendentalism of praxis" to critical empiricism in the 1960s and 1970s proceeds in two directions. On the one hand, he calls into question the traditional "Kantian" division of the skeptical currents advanced by Victor Brochard, highlighting their historical and theoretical interconnections with the grounds for previous philosophical reflection (the Socratic, Megaric, and Stoic schools); on the other hand, he determines the realistic foundation of skeptical negation and connects it with its phenomenalism of knowledge. Therefore, especially in their later phase, the skeptical positions appear to be guided by a specific logical setting for the criticism of knowledge that Dal Pra detects both in the awareness of different logical levels of argumentation and in epilogism. This is the skeptical attempt to overcome the absolute negation of truth for a "philosophy of experience", which will find its fulfillment in David Hume’s moderate skepticism and even in some theological advances in Johannes Scotus Eriugena’s agnosticism.
Keywords: Skepticism, phenomenalism, epilogism, experience, knowledge, negation