Of course, it pays to be cautious when you read philosophers writing about what exists. They are slippery, weaving in and out between “in one sense” and “in another” like clever eels wearing togas. The fact that we can talk about what doesn’t exist has long been a problem for philosophers: for what are we talking about? Surely what doesn’t exist must exist in some sense!
So, of course, in one sense just about anything we can talk about exists: it exists even just as a concept, or a figment, or a thin abstraction, or some ghostly possible being. But, in another sense, when we really get down to it, and wrestle to the ground the protean stuff that really does exist — the stuff that even God would be forced to recognize as existing (that is, if God really did exist) — well, there’s not as much of it. We can talk about more than there is.