If you have read any of The Discourses of Epictetus you have encountered his thoughts on preconceptions and they being the cause of “all human ills” (Epictetus, Discourses 4.1.4.2). Given that for much of Discourses his focus is on the three disciplines (Assent, Action, Desire) it is strange to see so much focus being given to this as the cause of all ills. However if we understand what a preconception is in Stoic philosophy and the role it plays in the use of impressions we get a feel for why so much weight was placed on the notion of preconceptions.
Preconceptions, are judgments of impressions that exist prior to experiencing the impression. That is a lot of jargon in one sentence so I will try and explain in more modern terms. A preconception is in a nutshell ideas formed about some thing before experiencing that thing.
It may be helpful instead to have an example of a preconception. Suppose you are walking in the park and you see a man jogging along. You see the sweat in his shirt and his heavy breathing and you say to yourself, man that looks like a lot of work. What you have done without thinking is applied a preconception. In this case, that preconception is that sweating and breathing heavy are negative things. From his perspective however he may be enjoying the run and the sweat and deep breathing bring him joy.
The takeaway from this is that when we are judging impressions in our daily life we must remember that we often bring bias and opinions that we do not realize to the table. Our preconceptions influence what impressions we give assent to, so care must be taken to apply those preconceptions carefully and with intent. Further we must understand that others bring their own to the mix and often they are at odds with our own. This is why so much emphasis is given to their application. Part of Stoic philosophy is examining our preconceptions and refining them and their application through reflection and study.
With gratitude and respect,
Todd, Derrick, Kathryn