Full Idea
They include the study of canons and criteria in order to discover the truth. This is to straighten out the differences among the presentations. And they also include the definitional part for the purposes of recognising the truth.
Clarification
'presentations' are appearances
Gist of Idea
Stoics study canons, criteria and definitions, in order to find the truth
Source
report of Stoic school (fragments/reports [c.200 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 07.42
Book Reference
'The Stoics Reader', ed/tr. Inwood,B/Gerson,L.P. [Hackett 2008], p.11
A Reaction
Might we call this categorisation, justifications and definitions? This is part of the study of logos, which comes first in the stoic view of philosophy.