Nominal essences are all the essences that science needs, and some are better than others, because they capture more regularity in nature.
To explain: a "nominal essence" is just an abstract idea that humans have decided to use to pick out a particular type of thing. This is contrasted with a more Aristotelean view of essence.
Because I'm curious:
Is Dennett's position intended to be a response to the theory of scientific incommesurability, or some other aspect of philosophy of science?
Here's the new thread for posting quotes, with the usual rules: