It is widely thought that first possession is the original basis for property rights. But this opinion leaves open the question, what constitutes “possession”? This article analyses the common law understanding of possession as an act or series of acts that signal an intention to exercise control over some object or resource. This legal understanding means that acts of possession are fundamentally a kind of communication. Once one sees legal possession as a form of communication, several things follow. First, property claims take place within a culture of people who understand the signals. Second, people in other kinds of cultures might not understand the signals, and this fact can lead to clashes about resource uses. To some degree this was the case between European settlers and American indigenous peoples in 19th century, where Europeans thought that certain possessory acts (especially farming) should give them a property right in land, but Native Americans did not agree with this claim to property.