In act I of "The Crucible", why did Putnam oppose Proctor?

In Act 1 of "The Crucible", Miller introduces the problems between the characters of John Proctor and Thomas Putnam.  These problems foreshadow the problems that will occur shortly after this introduction. The problems that the two men have are based on land and the ownership of land.  The land problem will be the root of much of the conflict introduced into the play.  In Act 1, when Proctor goes to leave, he speaks of working on his land and retrieving firewood for his family. Thomas Putnam retorts by asking what land Proctor plans to take that wood from. Proctor states that it is from the land he just purchased whereas Putnam claims that he had no right to buy this land because the seller never owned it and therefore did not have the right to sell it.  Giles Corey then pipes in and says that Putnam's father was in the habit to drink too much and will his land away, land that was never his.  This prompts the fight between the two men.  Later, Putnam will have his daughter and wife accuse other women of witchery to try to claim their land after they are hanged.