Full Idea
The Stoics distinguished between logos prophorikos ('uttered reasoning') and logos endiathetos ('reason stored within').
Gist of Idea
The Stoics distinguished spoken logos from logos within the mind
Source
report of Stoic school (fragments/reports [c.200 BCE]) by Plotinus - The Enneads 5.1.03 n7
Book Reference
Plotinus: 'The Enneads', ed/tr. Mackenna,Stephen [Penguin 1991], p.350
A Reaction
These seems required, since logos is often the 'giving of an account', but it is also the rational principle that rules nature.