"Angels, not being material, are pure forms or essences on Aquinas's view, but even with them their essence needs to be combined with existence in order for them to be real, so that they too are composite."
He then complained:
Putting aside whether parsing the nature of angels could ever be rational, how could anything be both "pure" but also a "composite"? Professor Feser's muddled book is rife with this sort of linguistic deviance.
In response, one reader added:
Angels are pure "essences"? What does that even mean?
I can't help thinking about Gen. Jack Ripper in Dr Strangelove and his obsession with Purity of Essence and the need to protect it by starting a nuclear war.
The passion people pour into meaningless phrases continues to amaze me.
Sigh. You'd think the Middle Ages had never happened. Good thing for those hoary old Scholastics they never had to face down such mighty objections.
Two is a pure form, a purely formal object, the essence of which is strictly independent of any material instantiation of it. Once "2" gets written on paper or typed onto a computer screen, however, it is "dematerialized" and thus becomes a composite of a '2'-essence and a materially specific existence. Every instance of "2" instantiates the essence of 2, but no composite instantiation of it in material existence exhausts the essence of two, since it can always be instantiated in its essential purity by some other material instance. That is, we can't say this instance of 2 is "more truly" 2 than that instance of it; they both enjoy the identically pure essence of 2, but do so in materially, compositely specific ways as they happen to exist. Hence, while a written "2" enjoys a composite existence, it does so by virtue of the pure essence of 2 informing the matter involved.
The same goes, although even more vividly, for all formal operations, such as addition, subtraction, modus ponens, and so forth. Every instance of such formally pure operations enjoys a composite existence when it is dematerialized, but no physical set of instantiations can exhaust the essentially pure formality of any such operation. Hence, any physically instance of a formal operation partakes of a formally pure reality that exceeds the power of physical computation. Any instance of, say, addition could always be challenged and revised as but a covert case of "quaddition." Kripke, Goodman, the grue problem, etc.
To get the full story, read James Ross's "Immaterial Aspects of Thought" here