Full Idea
That is not the same whole that does not have the same parts.
Gist of Idea
If parts change, the whole changes
Source
William of Ockham (Commentary on the Sentences [1320], IV.13), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 29.2
Book Reference
Pasnau,Robert: 'Metaphysical Themes 1274-1671' [OUP 2011], p.693
A Reaction
In isolation, this is mereological essentialism (as Pasnau confirms), which is incredibly implausible, if I cease to be the same person when I cut one of my fingernails.