Full Idea
A trout-turkey is inhomogeneous, disconnected, not in contrast with its surroundings. It is not cohesive, not causally integrated, not a causal unit in its impact on the rest of the world. It is not carved at the joints. That doesn't affect its existence.
Gist of Idea
Trout-turkeys exist, despite lacking cohesion, natural joints and united causal power
Source
David Lewis (Parts of Classes [1991], 3.5)
Book Reference
Lewis,David: 'Parts of Classes' [Blackwell 1991], p.80
A Reaction
A nice pre-emptive strike against all the reasons why anyone might think more is needed for unity than a mereological fusion.