 That anyway is how those in favour of matter-involving forms take this passage, but there is another possible reading. Instead of failing to realize that human beings, unlike circles, are essentially realized in flesh and bones, and as such these must be included in their form, Socrates the Younger’s mistake might have been his paying insufficient attention to the fact that circles, being mathematical objects, need not be instantiated in any specific kind of matter at all, whereas human beings always are. If this is the mistake that Aristotle is identifying, this passage would not support any sort of matter-involving forms, but only the view that natural forms, like the form of a man, are always instantiated in matter of certain sorts. Even if the forms were necessarily so instantiated, this would not require that the matter be included in the specification of the thing’s form.