Monism

Monism is the philosophical stance that there is only one kind of matter, and that phenomena such as the mind can be explained in terms of interactions within this one type of matter. Materialism is a form of monism as it states that only matter exists. Note that 'matter' in this sense does not mean quite the same thing as it does when we are discussing science: forms of energy such as light photons are also "material". Pantheists and Idealists can be seen as monists.