I think you might have it a bit wrong there.
The secondary reality is a subset of the primary, that is it exists within it; the primary can exist without the secondary but that the secondary reality could not exist outside of the primary (as far as we know). Due to this we can only assume that the secondary is a product of the primary; some element within the primary must be a basis from which the secondary comes.
I'm not sure how relevant it is, but I always found facts like it when discussing things like this:
The wavelengths of light to which our photo-receptors are sensitive covers less than 1% of the total spectrum. This is not to say that these other wavelengths are not present or any less common however. We are constantly surrounded and subject to a practically infinite amount of electromagnetic radiation, 1% of which is enough to create everything we see, know and base our consciousness on. Whether or not that is an illusion is immaterial once you consider what a tiny proportion of actual reality it is.
What's up BullDog?
Did I write somewhere that the primary is a subset of the secondary? If I did then it was a mistake and yes, it is obviously the other way around. Something primary can't be a subset of something secondary.
Yes, we live in a world of practicality, not fact, and we ignore so much that is "known" in this secondary world.
Just think about how many beliefs and assumptions are the truth for us, when we have never directly experienced these things ourselves.
Take atoms for example. Have any of us ever directly observed an atom? Only as a model, maybe. That model is obviously NOT the atom, but we start to believe that an atom is like that model.
This happens to too many things to mention and this gets us into a lot of trouble.