Full Idea
One might wonder if it is possible to use each thing both for its natural purpose and otherwise - and that as itself or incidentally. E.g. twisting an eye so that one thing appears two, but also using an eye as something to sell or eat.
Gist of Idea
Eyes could be used for a natural purpose, or for unnatural seeing, or for a non-seeing activity
Source
Aristotle (Eudemian Ethics [c.333 BCE], 1246a26)
Book Reference
Aristotle: 'Eudemian Ethics I,II and VIII', ed/tr. Woods,Michael [OUP 1992], p.35
A Reaction
The important idea here is the core notion that there is a 'natural' purpose. Sceptics might say that all purposes derive from how a mind wishes to use something; otherwise there would be processes, but no 'functions' or 'purposes'.