Rex and Bella

About this video

Ana's dog Rex is small and brown, with short legs. Her neighbour's dog Bella is huge and white, with long legs. Rex and Bella look far more different from each other than Rex and the neighbour's brown cat do. Yet everyone says Rex and Bella are both dogs and the cat is not. What makes two things the same kind of thing?

Rex is one thing; "dog" is a group that Rex, Bella and millions of others belong to. A group like this, whose members share something, is called a kind: gold is a kind, and so are tigers, chairs and rain. Some groups are clearly made up by us, like the things in Ana's pocket today - a key, a pebble and a sweet - which have nothing in common except where they happen to be. Tigers seem different: they were tigers long before anyone named them. So are all kinds like the pocket, or are some really there in nature, waiting to be found?

One answer: some kinds are found. Rex and Bella share something real even if you can't see it - they come from dogs and can have puppies together - and gold is gold because of what it is made of, whatever we call it. Plato wrote, about 2,400 years ago, that good sorting cuts nature "at its joints", like a skilled cook carving where the joints are. Its puzzle: where is the kind? You can stroke Rex and Bella, but not "dog". The other answer: all kinds are made. There are only single things, and we sort them because it is useful; different people sort differently - some languages use one word for green and blue. Its puzzle: how could we ever find out we sorted wrongly? People once called whales fish, then learned that whales breathe air and feed their babies milk. That feels like discovering something about the world, not changing a word.

This video goes with the Kinds of Things lesson of Metaphysics Level 1 on Knaph.

Transcript

1. 0:00Rex is small and brown. Bella is huge and white. Both are dogs.
2. 0:05Dog is a kind. The things in Ana's pocket are just a pile.
3. 0:11One answer, some kinds are found in nature. The other, all are made by us.
4. 0:17But where is dog? You can stroke Rex, not dog.
5. 0:23And whales were called fish, until people found they weren't.
6. 0:29Do we find kinds, or make them?