Do non-mathematicians spawn mathematical ideas?
What's an example of an idea that exists almost everywhere and at all times?
Sure, before there was formal "math" as we'd call it, Egyptians and many other cultures were able to do some pretty mathematical things. I mean, I guess in that sense, they were mathematicians, but there was no such thing as formal math, so what they were doing was really instinctively (or subconsciously) preforming mathematical operations? Perhaps in the same way that, say, a basketball player doesn't consciously preform the mathematics of the requisite arc needed to reach the basket with the ball. But in the sense, they reflexively (instinctively?) do just that. So, now I really have no idea what a mathematician even is anymore...
I believe he is talking more about mythological, i.e. psychological phenomena though. For example, the "engendering" of psychic phenomena (as male or female), or even just the universal
experience of the numinosum, even if in form of different psychological symbols. The work from which I took the quote pretty much presupposes that you have already become familiar with Jung's earlier work on archetypes and so pretty well agree (by continuing to follow Jung's thought process through) that they are real. This is just part of what makes it so difficult to understand a great deal of his work. In addition to it simply being rather complicated in and of itself...