The idea that there are two incompatible realms: matter and spirit. Traditionally, dualism holds that Spirit is good and Matter is bad. This is the case in Neo-Platonism, Hinduism, Buddhism, and many denominations of Christianity that are influenced by Neo-Platonic thought.
The idea that all things are God and God is all things. Note, this is distinct from the idea that God is in all things. Rather pantheism sees that all things are God/Spirit. There are elements of pantheism in Hinduism, Wicca, and Pagan religions.
The idea that there is no spiritual, invisible realm. All that exists is what we can see. This is typically the idea held by secular humanists and atheists.
The idea that both spirit and matter are real and equally valuable. They can both be corrupted or both be good. The world and people are not divided entities, but made up of both the physical and the spiritual. They are not the same, but they are both present and both necessary. Though Christians have often tended toward dualism, Jesus taught holism.
What do you think about the nature of the world? How does that affect the way you treat people?