The "canon" is the measuring tool given by Nature against which we compare our thoughts and speculations to decide if they are consistent with reality and with our feelings of pleasure and pain
I found this sentence interesting and I don't know if problematic. I really hope I won't misinterpret you, Cassius.
Is there an assumption that Nature gave us tools to know the world?
I've read that from an evolutionary point of view (which I think is plainly consistent with epicurean philosophy) is problematic to think that some of our capacities evolved to have knowledge of the world. Specially because knowing the world (in a complete, maybe platonic way) is not something that we needed to survive.
From this perspective (I read it in a book called "The enigma of reason" by Sperber and Mercier), as primates, and before as mammals, we needed fast, or automatic, cognitions (we can include pattern recognition, for example) in order to survive. But as a social species, we developed different capacities that include language (verbal, visual, etc.) and a capacity to convince others (give reasons and make rationalizations). None of this capacities is designed (I mean, being the product of the mechanisms of natural selection) to know truths of the world.
I think my point is just to observe the assumption that Nature gave us tools to know the world, because precisely Epicurus tried to reject the existence of purposes in Nature (or maybe not and I'm misinterpreting Epicurus 🙈). And also I thought this could be relevant, or at least interesting.
In response to this:
I think we probably ought to be clear on this word since we are using it so often. Is it an exact synonym of "thinking" or of "consciousness" or what ?
In contemporary discussions there's a distinction between fast and slow cognitions (also called system 1 and 2, respectively) and is accepted in several disciplines (you can see more in "Thinking fast and slow" by Daniel Kahneman).
I hope this helps.