Qualitative Reasoning

[gusl]

Qualitative Reasoning seems to be about reasoning with abstract or vague knowledge (i.e. uncertainty). I think it's only needed because there would too many models (in the logic sense) for a probable worlds approach to be feasible (the same reason why non-monotonic reasoning might be necessary... I used to not like non-monotonic reasoning: you could say I was a Cheesemanian).


http://www.cs.utexas.edu/users/qr/book/ from here:

This book presents, within a conceptually unified theoretical framework, a body of methods that have been developed over the past fifteen years for building and simulating qualitative models of physical systems (bathtubs, tea kettles, automobiles, the physiology of the body, chemical processing plants, control systems, electrical circuits, and the like) where knowledge of that system is incomplete. The primary tool for this work is the author's QSIM algorithm which is discussed in detail.

I like the idea of qualitative differential equations. Many of my intuitions and arguments about economics are based on such things.

For example, the principle of decreasing returns is one where the utility function 'U(w)' of the work 'w' satisfies:
U is always positive and
U' is always positive
but U'' is always negative

I find it really cool to be able to draw conclusions from such abstract principles. Maybe this is related to my liking of proofs that use fundamental constraints (e.g. symmetry, information theory) or abstract philosophical assumptions (e.g. the world is a computer).