Full Idea
If some man kept the old planks as they were taken out, and by putting them afterwards together again in the same order, had again made a ship of them, ...there would have been two ships numerically the same, which is absurd.
Gist of Idea
If a new ship were made of the discarded planks, would two ships be numerically the same?
Source
Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.11.07)
Book Reference
Hobbes,Thomas: 'Metaphysical Writings', ed/tr. Calkins,Mary Whiton [Open Court 1905], p.85
A Reaction
This is the origin of the famous modern problematical example of the Ship of Theseus. The ancient example is just the case of whether you step into the same river, but using an artefact with parts, to make it clearer.