Existence is a property, it's just not what is wrong with the ontological argument.

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Just my interpretation. To briefly speak to the OP, and much like Pfhorrest, my opinion is that Kant used the term 'predicate' loosely as a mantra to poke-holes in the ontological argument (a priori/analytical judgements-of course). And that his ongoing mantra (critique) is simply to expose the inescapable truth that we can never really know existing things-in-themselves (and the true nature of their/our existence) through pure reason alone-a priori. Accordingly, he taught math, and believed that there were limitations to such a priori truths... .

Thus, from Pfhorrest's quote: "What Kant meant was that existence isn't a property of a thing. It's not like you can give a list of all of the properties of a thing and "existence" will be one of them. It's even more the case that you can't bake "existence" into the analytic definition of a thing"

Kant was right when he basically said existence can never be conceived by reason alone. (As you've stated, I think you already know that- 'the synthetic a priori'- but just wanted to offer another opinion to maybe arrive at some consensus here.)

His attack was on analytical philosophers... . — 3017amen

Yep, I guess Kant's critique of the ontological argument does depend on the analytic-synthetic distinction, the existence of god being, according to him in my opinion, a synthetic proposition whose truth is not contained in the meaning of the ontological definition of god as the greatest being imaginable.

Imagine a sphere and the predicate red. The sphere is different to the sphere if it is red i.e. the predicate red changes the sphere from just a sphere to a red sphere and the two are now different.

If existence is a predicate then, similarly, the addition of the predicate existence to an x should change that x to something different. x is then no longer the same as (x + existence), just like the sphere is different to a red sphere. Now if I say that the sphere is red, I'm not talking about the original sphere which was not; similarly, if existence is a predicate, if I say x exists I'm not referring to the original x. While this seems completely reasonable for the case of the sphere it's quite obviously wrong when I say that when I claim "x exists" I'm not talking about x.

Sure. That is where he uses the word predicate as "concept" instead of the literal meaning of an action word/verb.

Similarly, imagine a spinning ball in space or otherwise... . The ball is black on one side, and white on the other. But when it's spinning, all we see is a color somewhere between the two; a mottled color of grey. If we knew how to stop the ball, we would know its true color(s).

So to quote Kant directly:

"Being is evidently not a real predicate, or concept of something that can be added to the concept of a thing".

So to quote Kant directly: "Being is evidently not a real predicate, or concept of something that can be added to the concept of a thing". — 3017amen

What Kant said, sounds very similar to what Carnap's diagonal lemma suggests about a legitimate existence predicate:

it would need to be possible to detect it (or "add it") in a thing that does not exist.

That is a problem, because a thing that does not exist, cannot have predicates.

If existence were a legitimate predicate, Carnap's diagonal lemma insists that there will be things that do not exist but for which the existence predicate will still be true.

It is incredible that Kant discovered this without using any diagonalization.

Existence is a property, it's just not what is wrong with the ontological argument.

In layman's terms, this may help some:

That is a problem, because a thing that does not exist, cannot have predicates. — alcontali

Hey Alcontali, your quote got me to thinking about Intuitionism:

"...while other philosophies of mathematics allow objects that can be proved to exist even though they cannot be constructed, intuitionism allows only mathematical objects that one can actually construct."

https://en.wikipedia.org/wiki/Intuitionism

Of course in thinking about it all, the question of whether mathematics is a human construct, or whether it is something already existing 'out there' rears its head... . One thing we do know is that; it is timeless a temporal, Platonic, metaphysical, a priori etc. much like the human concept of God.

Of course in thinking about it all, the question of whether mathematics is a human construct, or whether it is something already existing 'out there' rears its head... . One thing we do know is that; it is timeless a temporal, Platonic, metaphysical, a priori etc. much like the human concept of God. — 3017amen

My own intuitive belief is that the abstract, Platonic worlds of mathematics exist regardless of humanity, which only discovers them.

Concerning existence as a predicate, if existence were a predicate, something that does not exist would have the predicate of non-existence, i.e. the negation of the existence predicate, but that is not possible because something that does not exist cannot have any predicates at all.

Carnap's diagonal lemma generalizes and systematizes that observation for all predicates. That is why it is such a good litmus test for figuring out if a property is truly a predicate.

Yep, I agree. That's my belief as well...that we didn't invent mathematics as a human construct but rather we discover and uncover it's truth... .

Do you have any good links for Carnap?

Thanks

Do you have any good links for Carnap? — 3017amen

The reference section in Wikipedia's page on the diagonal lemma is quite good.

I never really read his other work, as mentioned in Carnap's biography page at Wikipedia, because it does not seem to play the outsized role anywhere that his diagonal lemma does:

The sentences whose existence is secured by the diagonal lemma can then, in turn, be used to prove fundamental limitative results such as Gödel's incompleteness theorems and Tarski's undefinability theorem. — Wikipedia on Carnap's diagonal lemma

Concerning existence as a predicate, if existence were a predicate, something that does not exist would have the predicate of non-existence, i.e. the negation of the existence predicate, but that is not possible because something that does not exist cannot have any predicates at all. — alcontali

Very interesting. Now I know this is getting on slippery ground, but on first glance it seems like the products of our imagination have predicates. E.g. The word "unicorn" refers to an imaginary mythological creature that has various imaginary properties.

Now I know this is getting on slippery ground, but on first glance it seems like the products of our imagination have predicates. E.g. The word "unicorn" refers to an imaginary mythological creature that has various imaginary properties. — EricH

Yes. Unicorns exist in their imaginary world.

You can construct an imaginary world by describing it. For example, the imaginary world of Star Wars.

The difference between these imaginary worlds and the abstract, Platonic worlds described by mathematics is very, very subtle.

A Platonic world described by a mathematical theory stands a chance of being consistent.

If it is simple enough, it can even be provably consistent and complete. If such Platonic world has an infinite size and a little bit too much support for arithmetic, then it will be either inconsistent or incomplete, and you will not be able to determine which one it is: inconsistent or incomplete.

The imaginary world of unicorns or Star Wars does not stand a shadow of a chance of being consistent. The reason why this may not be immediately apparent, is because you cannot interactively interrogate it. If you could, it would almost surely promptly fall apart.

If any imaginary world is entirely consistent, then it is effectively an abstract, Platonic world that is part of mathematics.

My understanding of what Kant meant is rooted in my interpretation of Heidegger's response to the same question as set forth in Basic Problems of Phenomenology.

First, by existence Kant means "actual" as in currently existing in time. In that sense, that an object "exists" simply means that it has a location in space. And where an object is located would generally not be considered a quality of the object.

Second, by "real" Kant essentially means having primary (and presumably) secondary qualities. And if one were to make a list of Aristotelian or Lockean qualities as applied to the realness of objects (such as color, shape, weight) "existence" or "location" would not be on the list. For example, whatever qualities are essential for a book to be book, where the book is located will not be one of them.

So in that sense, the color, shape and weight of my auto would all be considered qualities while the fact that it currently exists in my driveway would not be considered a quality. The qualities are real predicates of the car while its location is not.