Book IX · 25

Examine into the quality of the form of an object, and detach it altogether from its material part, and then contemplate it; then determine the time, the longest which a thing of this peculiar form is naturally made to endure.

Go straight to that which makes a thing what it is, its formative cause, and, isolating it from the material, regard it so. Then mark off the utmost time for which the individual object so qualified is calculated to subsist.