Full Idea
In the case of a house, where the process of compounding the parts is obvious, though the parts exist, there is no reason why the whole should not be non-existent, and so the parts are not the same as the whole.
Gist of Idea
In the case of a house the parts can exist without the whole, so parts are not the whole
Source
Aristotle (Topics [c.331 BCE], 150a19)
Book Reference
Aristotle: 'Posterior Analytics and Topica', ed/tr. Tredennick,H/Forster,ES [Harvard 1960], p.637
A Reaction
Compare buying a piece of furniture, and being surprised to discover, when it is delivered, that it is self-assembly. This idea is a simple refutation of the claims of classical mereology, that wholes are just some parts. Aristotle uses modal claims.