Well, "owning" an item really means you can defend it, or you have some sort of factor that prevents others from taking it. In an extremely basic world, violence is going to be the only way to defend your "possession". Is it really self-defining it when you can defend the possession? Something that hurts someone else is very defining to others, I think. Although the rest of the things you said are very true, I just think that saying that the only thing you really need to do is stand there and label it "mine" is a little short. You have to back up the claim with a way to defend it.
Indeed, it certainly helps to have a gun when you're informing others that this is
your land, not
theirs. But that is an interaction with others. The connection that is
self-satisfying is the connection to the actual object possessed--your having a gun really has nothing to do with how you interact with that land.
Consider why it is that possession is the only form of interaction that must be defended in some way--a gun is not necessary to affirm that you made an object, know an object, or use an object. That is because all of these are defined by interactions with that object. Possession, however, is not an interaction with an object; it can only be defined (when it is) by an interaction with others--namely, others cannot interact with that object except by your assent.
All of this said, the problem with materialism -as a state of mind- is that it is an attempt to interact with the world through possession; this, on its own, is not possible, and it brings us to the position that we can own the world yet have no idea how to work with it.
Rhythm of Apathy said:
People certainly don't need a lot of the things they have, but I'm not entirely sure I can disagree when it's said that Materialism is the key to Power.
Ownership and power are synonymous in today's society and probably always has been. With enough money you can practically get anything, minus those sentimental things, but can't they be classified as a need anyway?
Materialism is the key to Power by common consent--power lies where it is believed to lie. However, as brought up by Sir Meta Knight, materialism (reduced to possession or ownership) is itself entirely dependent upon another factor--the ability to defend possession. So, it could be argued that possession of the world is nothing if one cannot use a gun.
To address Geocillin's take, I regard the philosophy of materialism in a similar light to nihilism--a sometimes useful starting point, but limited in potential for itself.