Full Idea
The cause of all human ills is that people are incapable of applying their general preconceptions to particular cases.
Gist of Idea
All human ills result from failure to apply preconceptions to particular cases
Source
Epictetus (The Discourses [c.56], 4.01.42)
Book Reference
Epictetus: 'The Discourses, The Handbook, Fragments', ed/tr. Gill,C [Everyman 1995], p.230
A Reaction
I'm not sure whether 'preconceptions' is meant pejoratively (as unthinking, and opposed to true principles). This sounds like modern particularism (e.g. Jonathan Dancy) to the letter.