Most property professors spend a lot of time early in the course asking when somebody acquires an unknown resource. When they do so, they have two agendas in mind. One is to ask as a policy matter in what circumstances is it appropriate for somebody who does not yet have rights in a resource to then claim rights that have priority over the rights of everybody else who might have gotten that resource too. Then the acquisition doctrine then answers much more specific questions - if we're talking about fox pelts, if we're talking about land, if we're talking about an idea. What are the doctrinal details you need to master to know whether one person has acquired prior access over this resource to the exclusion of everybody else? The acquisition lets us focus both on the doctrinal details about particular resources, and it lets us tackle high level questions about why have property at all. Why not let resources be in a free for all where anybody could get them? I guess then let me start with the higher level questions. In the tradition, there are two main sets of answers to the question if a resource is unowned, why give someone prior access? One answer comes from Locke, and Locke's answer is labor. If one person does work to find a resource and then incorporate it into his life plans and uses it then to make his life better, the search, the effort, and then most important, the use of the resource for that person's wellbeing give that person a reason to tell everybody else, "I'm now using this. You go find other things that are not yet owned and use those for your own wellbeing." This process of undertaking purpose of work to make one's own life better and incorporating a resource into that purpose of work, that's labor. The other justification for having property comes from Grotius and Pufendorf. Grotius and Pufendorf talk about possession, and possession, it's conduct that signals to other people that you've done something to signal, "I now have incorporated this thing into my projects. Stay away." Law professors and philosophers like to ask which is more important, labor or possession? I think the answer is they're both important. They're two different ways of focusing on the same kind of behavior. They're just focusing on different implications of the behavior. If you have a resource, the resource is going to implicate the person who ends up with property and then all the people who are going to owe duties to the person who ends up with the property. When somebody starts laboring on a resource, it's not quite enough to say, "I'm going to make my life better to do so." The person also needs a signpost to communicate to others, "I'm taking this thing out of the commons. I'm going to start using it for my benefit, and I've given you enough notice that it's now reasonable for you to go somewhere else." Then in acquisition doctrine, you see this play out. The trial acquisition doctrines tend to focus on simple behavior that seems to focus on possession. Have you occupied land? Are you farming it, or have you put a fence around it? Have you captured a resource? If you've invented a new idea, have you invented it? Are you using it? Are you keeping it secret? Those are all things that focus on possession. Possession in simple contexts, it's a twofer because conduct like capturing, fencing, keeping secret, it's claiming possession, but 999 times in 1,000 you expect that the person who has possession is also going to labor in a productive way with the resource.