As I said, he assumes there is some objectively correct way to define the “thingspace” and a probability distribution on it. Should this rather strong assumption hold, his argument seems plausible that categories (like “mortal”) should, and presumably usually do, correspond to clusters of high probability density.
(By the way, macrostates, or at least categories, don’t generally form a partition, because something can be both mortal and a biped.)
So I don’t think he takes certain categories for granted, but rather the existence an objective thingspace and probability distribution which in turn would enable objective categories. But he doesn’t argue for it (except very tangentially in a comment) so you may well doubt such an objective background exists.
I think some small ground to believe his theory is right is that most intuitively natural categories seem to be also objectively better than others, in the sense that they form, or have in the past formed, projectible predicates:
A property of predicates, measuring the degree to which past instances can be taken to be guides to future ones. The fact that all the cows I have observed have been four-legged may be a reasonable basis from which to predict that future cows will be four-legged. This means that four-leggedness is a projectible predicate. The fact that they have all been living in the late 20th or early 21st century is not a reasonable basis for predicting that future cows will be. See also entrenchment, Goodman’s paradox.
Projectibility seems to me itself a rather objective statistical category.
As I said, he assumes there is some objectively correct way to define the “thingspace” and a probability distribution on it. Should this rather strong assumption hold, his argument seems plausible that categories (like “mortal”) should, and presumably usually do, correspond to clusters of high probability density.
(By the way, macrostates, or at least categories, don’t generally form a partition, because something can be both mortal and a biped.)
So I don’t think he takes certain categories for granted, but rather the existence an objective thingspace and probability distribution which in turn would enable objective categories. But he doesn’t argue for it (except very tangentially in a comment) so you may well doubt such an objective background exists.
I think some small ground to believe his theory is right is that most intuitively natural categories seem to be also objectively better than others, in the sense that they form, or have in the past formed, projectible predicates:
Projectibility seems to me itself a rather objective statistical category.