For example, he mentions Kelley’s critique of the second way by saying he imports a Fregian notion of existence that Aquinas would not have shared. So, even though Frege’s notion of existence might be a good one, you can’t tell from the book because Feser can’t get into the details of Frege’s philosophy. I guess my point is that you would have to attack Frege’s notion of existence itself in order to defeat Kelley’s point.
Hmm. I would qualify in a couple ways.
(1) To dispute Kelley’s point (which I don’t fully remember, and I don’t have
Aquinas on hand) it is not necessarily the case that Feser must defeat Frege’s notion of existence, but just that Feser shows that Aquinas’s analysis of existence is legitimate. If Frege’s notion of existence is the only notion, then it would cause issues for the Second Way.
(2) Frege’s analysis is of second-order predication of existence, ie. existence as concept instantiation. I don’t think we should reject Frege’s position with regard to second-order predication; I think we need it if we are to understand propositions such as “There are cats.” The difference comes in when we say, “Oscar (a cat) exists.” The first-order usage is more natural here, though the Fregean/Russellian view is that it ought to be read also as a second-order usage. But I think that the reasons for this are pretty weak. (Many of the concerns stem from the idea that to allow the first-order usage will require that when we say, “Garfield (a cat) does not exist,” we are attributing a real property to a thing which does not exist, which is absurd. But this seems to ignore the possibility of parasitic reference and that allowing existence as a real predicate does not entail that non-existence is a real predicate.)
(3) Though it takes some work to dispute the idea that only Frege’s analysis is legitimate, it’s worth noting that Aquinas’s argument for the essence/existence distinction would serve as an alternative (though not necessarily inconsistent) analysis.
A good book to read on the subject is
The Fullness of Being by Barry Miller. (It’s surprisingly readable considering the difficulty of the subject matter.) He accepts the second-order analysis of Frege and Russell, but argues that there are also legitimate first-order usages of existence and, consequently, that existence is (pace Kant) a property/predicate.
It’s worth noting that most of Scholastic natural theology would be in a lot of trouble if Frege’s were the only legitimate analysis. Anthony Kenny argued that the formula that “God’s essence is his existence” is equivalent to the proposition “There is one,” given Frege’s analysis. The point would be well-taken, if it made any sense to read Aquinas’s formula in Fregean terms.
. His