0:55 I'd disagree that existence is a property - existence is not a genus, since anything "supposedly" outside of that genus would not exist. "Nothing" or "non-existence" can not be reified. I'd agree that the essence/what-ness of a thing is a property of it, though argue that existence itself is not. Also, not to make an ontological argument (since I don't find them compelling) but in your unicorn example, I'd agree that unicorns have an essence, but I'd also argue that unicorns do exist, albeit only in the mind. Compare this to a square circle, something that does not exist in reality or in the mind. The two essential qualities we could argue a square circle having is "squareness" and "circleness", two qualities which are essentially contradictory. The square circle has no essence, and therefore can not exist, in the mind or reality.

Existence is both a noun and a verb depending on the on the usage. Existence is a property of reality. It acts like a feature, but it isn't mere accidental. The existence actualizes the essence with all its features, but because existence and essence are distinct, the existence lies over and above the essence.

I think one of the problems is that we are discussing concepts of things. People tend to put unicorns and horses in the same bucket and then talk about existing and not existing as though they are properties of the different things in the bucket, but the things in the bucket are not things, they are concepts. Concepts all have the same properties, independent of their referent. Whether or not a concept does or does not refer to something that actually exists seems like it has nothing to do with the concept itself, as they "exist" independently. I put that in quotes because concepts seem to be either actions that are carried out by, and contingent upon, brains or if they "exist" in any sense of the word it would be as synaptic constellations in the brain. Meaning if we consider memories existing things, they exist independently of the thing they are about, there is no actual link between them. All of that is to say the idea of some connection between essence and existence seems strange to me, because essence speaks to a concept, while existence speaks to a thing.

ok but so what

An essence's existence can't be an activity of the essence in the sense that the essence is logically prior to its activity of existing in the same manner that being a rational animal is logically prior to the activity of laughter. This is because an essence that is not composed with an act of existence is purely nothing at all. Existence is best conceived of as a first order predicate. It's not even accepted amongst all thomists that this argument you highlighted is an argument for the real distinction, Wippel thought that the real distinction was established in "stage two", Owens thought it was only established after a proof of God had been demonstrated, Knasas maintains this position too. Anyway, I'm inclined to think the argument works. If we can conceive of any contingent essence without knowing whether or not it exists, then either these essence are really distinct from their acts of existence, or they are merely conceptually distinct. However, the only ways in which two concepts could be distinct conceptually but identical in reality, I am inclined to think, are with respect to their relation to another concept or activity. For example, the morning star is conceptually distinct from the evening star because of the same stars relation to particular time periods of the day, when we conceptualise it. Additionally, I can conceive of Clark Kent without conceiving of his abilities to perform the activities of flying and saving people, because I am ignorant of his capabilities. I don't see how we could catégorise the distinction between esse and essence into these two types of conceptual distinctions, so the distinction must be real. Perhaps there is another manner in which two distinct concepts can be really identical, but if there is this is something I am currently ignorant of.

I think you’re being over-analytical and still dead wrong. The argument does exactly what it sets out to do. It makes a distinction between the idea of a thing and the existence of a thing. So what if he didn’t distinguish between whether what is being established in the latter part is the actual existence of a thing vs the acknowledgment of the existence of a thing.