> What's particularly neat about this is I can construct a pyramid of interests so [the foundation is fairly broad ... and narrows to the specialization](https://thoughtstreams.io/jtauber/journeyman-of-some/10772/) I'm interested in as you go up.

James, may we risk saying that **cosmology** generates one of your **principal ideal**s?


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Well, the irony is ring theory isn't part of the constructed background of interests for cosmology :-)

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Actually, I'm wrong, my constructed background *does* include the course "Groups, Rings and Modules" at Cambridge.


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BTW, huge points to [Dave](https://thoughtstreams.io/Dave/) for suggesting the light-cone as a more useful analogy in the context of cosmology.

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if speaking in terms of [Principal Ideals](https://thoughtstreams.io/jtauber/response-to-dave-about-principal-ideals/) is inconsistent, we could always press the cosmological background-cone into service.

Consider the interval between, eg **cosmology**, and any other concept: we can classify these intervals according to the following schema:

- consequential: one background cone contains the other.

- inconsequential: the background cones fail to intersect, or do so only partially.

- tangential:  one concept occurs on the boundary of the other's background cone.

I hope a trichotomous classification of intervals *is* consequential with regard to cosmology? :-)

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I love the idea of saying that, for example, "Vector Calculus is in the past light-cone of cosmology".

To more precisely relate his trichotomy to light-cones, I think you have:

* subject A is in the past light-cone of subject B
* subject A and B both have subject C in their past light-cone
* subject A and subject B are space-like

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I'd intended the [trichotomy](https://thoughtstreams.io/jtauber/response-to-dave-about-principal-ideals/10796/) to be:

- consequential / timelike

- inconsequential /spacelike

- tangential / lightlike

but it's been decades since I've dealt with the [molluscs](https://thoughtstreams.io/Dave/embalmed-ones/10804/) of space-time.