Clouds and eggplants

Cirrus clouds
Exactly how many clouds are in this photograph?
Image courtesy Dimitry B

Nebulosity is the central concept for In the Cells of the Eggplant. The book’s fundamental theme is “how does rationality relate to nebulosity, and how can we make that work better?”

Literally, nebulosity means “cloud-like-ness”:

Clouds are an extreme case, but nebulosity is pervasive. Other than in mathematics and fundamental physics, nothing is ever definitely this-or-that. Everything is always somewhat this and somewhat that. Put under high enough magnification, a stainless steel ball exhibits the same indefiniteness as a cloud. No ball can be perfectly round, nor made of perfectly pure steel, nor can one definitely say whether some particular atoms are part of it or part of its surrounds.

“Gray areas” are the easiest way to think about nebulosity. Is it true that maroon is a shade of red? Well, pretty much, although it’s a bit of a gray area.

Questions of degree do not exhaust nebulosity, though. Consider “yes, there is some water in the fridge: in the cells of the eggplant.” The problem here is not one of a gray area between water and non-water. Nor are we factually uncertain whether or not there is water in the fridge, so scientific investigation could answer the question. It is not that the word “water” has two different meanings, referring to two different kinds of water. It is that what counts as water depends on what you want it for.

Part One of The Eggplant explains in detail why there are no “really truly true truths” about eggplant-sized objects. Mostly, the best we can get is “true for all practical purposes.” And most of the truths we use, even in the hard sciences, are “pretty much true” or “true as far as a particular purpose goes.” This raises occasional problems for rationality in practice, and causes serious difficulties for rationalism as a theory.

Meta-rationality, the main subject of The Eggplant, addresses these issues effectively.