Ancient skepticism is often described as the view that nothing can be known. Its practitioners described it differently, as a practice whose aim was a settled mind.
The stated goal was tranquillity
Skeptical writers report that they began by seeking truth in order to resolve the disturbance caused by conflicting opinions. The search was undertaken for relief rather than for its own sake.
Finding the arguments on each side equally balanced, they suspended judgment, and reported that the disturbance subsided once the attempt to settle the question was abandoned.
The sequence matters. Tranquillity is described as following suspension unexpectedly rather than being achieved by aiming at it directly.
The method was balancing arguments
The characteristic technique is to set an argument against an equally strong opposing argument so that neither compels assent. The practitioner is left holding two positions of apparently equal weight.
Collections of such oppositions were assembled and organised, giving the tradition a body of material that could be applied to whatever claim was raised.
The aim of the technique is suspension rather than refutation, which distinguishes it from ordinary argument where one wants to win.
Suspension is not paralysis
The obvious objection is that someone who suspends judgment about everything cannot act. The skeptical reply is that action does not require certainty.
They described living by appearances, custom, natural inclination and instruction in a craft, none of which requires a settled view about underlying reality.
On this account the skeptic eats when hungry and follows local law without holding that either practice is grounded in demonstrated truth. Ordinary life proceeds on appearances, as it largely does for everyone.
It differs from modern skepticism
Contemporary usage often means doubting particular claims, especially poorly evidenced ones, which is a stance about evidence rather than a way of living.
Modern skepticism also typically asserts positions, which the ancient version treated as the very thing it was trying to avoid.
The vocabulary overlaps enough to cause persistent confusion, and a reader expecting the modern sense finds the ancient texts strange in ways that have nothing to do with their age.
The self-referential problem
Critics ask whether the skeptic asserts that judgment should be suspended, which would itself be an assertion of the kind being avoided.
The response was that skeptical statements report how things seem to the speaker at that moment rather than stating how things are.
Whether that reply succeeds has been argued about ever since, and it remains one of the more interesting places where a philosophical position tests its own consistency.