The Hellenistic Philosophers:

Socrates' legacy:

  1. Logic and Classification Stoics, Aristotle
  2. Virtue As The Primary Good Cynics, Stoics, Aristotle
  3. Insolence Epicureans, Cynics
  4. Only the Eternal can be Known First Academy

A Missing Piece

What about the Socrates who claimed to know nothing?

Enter The Middle Academy

  1. Arcesilaus (316-241 BC)
  2. Carneades (214-129 BC)

The Academic Skeptics

  1. Pyrrho of Elis (365-275 BC)

General features of skepticism

  1. Elenchus (vs. Dialectic)
  2. Suspension of Belief (Epoche)
  3. Tranquillity (Ataraxia)


Arguments go two ways.

From plausible premises, one can form a new belief.

From absurd conclusions, one can reject premises.

Rejection: Believing Not vs. Not Believing (Suspension, Epoche)

Dogmatic vs. Skeptical Philosophy

Both give arguments.

Dogmatists aim at belief.

Skeptics aim at Epoche.

Dogmatism and the Formal Modes

Basis of Knowledge

Dogmatists attempt to build knowledge up from prior knowledge. So either:

  1. For every piece of knowledge, there's a prior piece
  2. Some pieces of knowledge are not based on prior knowledge

If (1), then either we have an infinite regress, or a circle.

If a circle, then we cannot know unless we already knew.

But we wouldn't be asking if we already knew.

So we should suspend.

If an infinite regress, we can't know the conclusion until we know the starting point.

But there is no starting point.

So we should suspend

If (2) then we must base or knowledge on something that is not knowledge.

But such a thing must be an unsupported Hypothesis

Hence, we must suspend.

The Problem of the Criterion

How could knowledge be based on something that is not itself knowledge?

What about the senses?


For Epicureans, the senses are the primary criterion of truth.

  1. Cannot be mistaken, in some sense (a little mysterious).
  2. Reason's only role is to sort out disagreement.
  3. Non-evident is at the mercy of the sense.


For the Stoics, knowledge involves reason. Perception is nothing without assent. We figure out what the senses mean by induction and classification.

This lets us avoid error. But do we start on the road to knowledge?

phantasia kataleptike: cognitive impressions.

Cognitive Impression

That which

arises from that which is; is stamped and impressed in accordance with that very thing; and of such a kind as could not arise from what is not

(definition of Chrysippus)

The Skeptical Challenge

There are no cognitive impressions.

Two arguments:

  1. From Indiscernibles
  2. From Madness

The Stoic Reply

  1. Identity of indiscernibles.
  2. Different kinds of impressions can be subjectively indistinguishable.

Does (2) just capitulate?