In the course of debating free will I came across the question "Why a compatibilist definition of 'free will' but no compatibilist definition of 'Santa Claus' or 'leprechauns.'" At first I thought it was somewhat of a silly question, but then I gave it some deeper consideration.

We create constructs to explain empirical observations. "Santa Claus" is one such construct and arguably there is a compatabilist definition of Santa Claus (I don't mean the potentially historical Saint Nicholas).

Santa Claus is a construct used mostly by young children to explain the empirical appearance of gifts under a tree on the morning of December 25th. In some sense Santa Claus is not real because there is no fat man in a red suit navigating chimneys on Christmas Eve.

Of course, as any postmodernist can tell you no empirical object lives up to its ideal definition including tables, chairs, and computer monitors. These are all just piles of atoms that sometimes have the properties of these idealized objects. So in some sense tables, chairs, and computer monitors are not real either.

But gifts do appear under the tree. Something "real" is causing this empirical phenomenon. We could call that thing Santa Claus. In this case Santa Claus is the spirit of giving created by decades of tradition in Western European countries and places influenced by them.

And that is perhaps an actual compatabilist definition of Santa Claus. It is a construct that explains the empirical phenomena that were associated with Santa Claus.

Similarly, we may point to something like aurora borealis. "Aurora borealis" literally means "Northern Dawn." We know now that aurora borealis is not a northerly rising of the sun nor the emanation of divine power nor other older explanations of why there are lights in the sky of the North. Is it proper to say there is no "Aurora Borealis" because magnetic particles creating streams of plasma when interacting with the atmosphere is not the sun rising in the North?

I don't think so.