"That isn't particularly controversial because the 'existence' of even numbers is logically a very different thing from the 'existence' of dodo birds, or 500-foot-tall Schwinn bicycles, or Inspector Gadget."
That's a concept, what do you mean by existence? Does that mean Harry Potter and Inspector Gadget exist? I don't think you're using the word "existence" correctly. I may be wrong in knowing what you're arguing as it was hard for me to parse what you wrote. I'm sorry if I misunderstood it.
If I'm using the word "exist" wrong (which I am happy to admit) then I certainly want to learn how I should be using it, for sure.
For the record and hopefully to reduce confusion, I don't think that Inspector Gadget (the man) exists. But there is still something it would be for him to exist, presumably; it just doesn't happen to be true.
Suppose I tell you there is (exists) a cheeseburger in the bag. You want to know if that's true, so you look in the bag. What do you look for? Depends on what you expect a cheeseburger to look like: probably you expect a physical object within a certain range of sizes, with certain parts of certain compositions, etc.
Now same story but meatball sub. Well, the things to look for are different in some ways.
Now same story but even number greater than 10,000. There isn't a bag you can look in for this. etc.
Dodo birds used to exist, don't any more. Checking for them is pretty different from checking for numbers or cheeseburgers in a bag.
Sherlock Holmes never existed. But you probably have at least some idea what it would mean if he did, and this is tied to how you'd check to see if he did exist.
The idea here is that 'exists' doesn't seem (to me) to be one operator which always does the same thing; it seems to be very well bound to whatever it is we are talking about the existence or nonexistence of.
That's a concept, what do you mean by existence? Does that mean Harry Potter and Inspector Gadget exist? I don't think you're using the word "existence" correctly. I may be wrong in knowing what you're arguing as it was hard for me to parse what you wrote. I'm sorry if I misunderstood it.