Full Idea
Aristotle gives certain samples of 'hanging together', notably continuity, rigidity, uniformity, qualitative similarity, being of a like kind, being of like matter.
Gist of Idea
Wholes are continuous, rigid, uniform, similar, same kind, similar matter
Source
report of Aristotle (Metaphysics [c.324 BCE], 1015b05-) by Peter Simons - Parts 8.1
Book Reference
Simons,Peter: 'Parts: a Study in Ontology' [OUP 1987], p.292
A Reaction
Families are scattered, lakes aren't rigid, cakes aren't uniform, complex gadgets have dissimilar parts, two kinds can be united, and only boring things are made of one sort of matter. Nice try, though. Simons rightly adds causation.