Why would native american attitudes toward land ownership lead to conflict with europeans?

The Native Americans were never ready to sell their land permanently as they thought land was equivalent to life and so should never be sold. The Europeans on the other hand thought that they were buying the land from the Native Americans. The Native Americans sometimes gave the right to use to two different people for the same land. This again created confusion with the Europeans both people thought that the land belonged to them. This was the main reason for conflict between the Native Americans and the Europeans regarding land ownership.