A comment to “names are interfaces” in the weblog Erik Benson’s Weblog:

The following is my translation of a passage from a Swedish book I’ve just read, which reminded me of your post:

Every horse is different in some aspects from other horses, and every horse is in some aspects similar to other animals of other species. However, when we decide that all horses make a species, which is contrasted with other species, we choose to disregard from these differences, and to consider them uninteresting, especiellay in some situations. The tendency to see all horses as a specific species is reflected in language, simply because there is a term which is used to signify this particular species.

That we choose to ignore some differences is perhaps best illustrated with another example. There are obvious similarities between whales and fish. Yet we don’t consider whales to be fish. Instead we classify them as mammals, because they, contrary to fish, give birth to live young which they nourish with milk. The fact that this particular characteristic is considered more fundamental than those whales share with fish, and those which distinguishes whales from, for instance, land-living mammals, has to do with our biological theories […].

There are, however, according to Goodman, no way to classify entities that is given by nature itself. Whether a certain characteristic is more fundamental than another, and whether some differences are more relevant than others, always depend on our particular interests and views, and there are no classification independent of these parameters.

This is from Folke Tersman’s Fem filosofiska frågor (“Five philosophical questions”). He also points to a book by Nelson Goodman (who is mentioned in the above quote), Ways of Worldmaking, which he summarizes like this:

To articulate a particular worldview […] implies creating the world in which we live, and there is no world that exists independent of such creation. Despite that some such creations might be incompatible, Goodman thinks that all of them can be true. Therefore, there is a very strong sense to the idea that people can live in ‘different worlds,’ which goes beyond having different experiences and conditions for living.