Full Idea
If, for the sake of argument, someone were to mould a horse, squash it, then make a dog, it would be reasonable for us on seeing this to say that this previously did not exist but now does exist.
Gist of Idea
If someone squashed a horse to make a dog, something new would now exist
Source
Mnesarchus (fragments/reports [c.120 BCE]), quoted by John Stobaeus - Anthology 179.11
Book Reference
'The Hellenistic Philosophers:Vol.1 translations', ed/tr. Long,A. /Sedley,D. [CUP 1987], p.168
A Reaction
Locke would say it is new, because the substance is the same, but a new life now exists. A sword could cease to exist and become a new ploughshare, I would think. Apply this to the Ship of Theseus. Is form more important than substance?