One of the central philosophical desires from Plato through Descartes and until the Postmodernists was to find absolute certitude as opposed to the mere opinion that falls short of it. This desire makes no sense if we take “what falls short” as being just a little less of the same sort of stuff. In fact, if we take it in this way the desire for certitude can seem like an irrational fetish. “Certitude” or “being sure” first means fixity or adherence to some place – which is why mountain goats are “sure-footed” – and it would certainly be odd for mountain goats to spend millennia debating whether one could achieve a foothold so fixed that it would render a slip or a misstep a logical impossibility. A goat can surely do whatever it needs to do while being far less sure than this, and so can a mind.
But in fact what falls short of the certain is not just less of the same thing but a different kind of object. To fall short of the certain is to enter into the realm of doxa or opinion, which contains only concepts that are intrinsically at odds with themselves. Opinions both seem true and are taken as the basis of further thoughts and actions but acting on the basis of opinions requires taking them as if they were true and not as merely seeming so. We can only hold opinions by failing to treat them as such. Said another way, possible truths are apparent goods, and we can’t act for an apparent good as apparent.
(One confusion about this last point arises from the thought that possibility might be a motive for action. If we’re dying in the desert, and the image we see in front of us is possibly water or possibly a mirage, it would make sense to go towards it either way. But even in this situation we’re not going towards possible potable water. If such a thing sufficed to cause us to act, we would move toward a cloud, a tank of hydrogen gas, or a glass of known sea-water.)
Episteme and doxa are therefore not related like the gold-package deal to the silver package deal but as the actual object of thought and an object which, in comparison, seems to be constituted by a sort of hypocrisy of logic.