 Neutral monism is a monistic metaphysics. It holds that ultimate reality is all of one kind. To this extent neutral monism is in agreement with the more familiar versions of monism: idealism and materialism. What distinguishes neutral monism from its monistic rivals is the claim that the intrinsic nature of ultimate reality is neither mental nor physical. This negative claim also captures the idea of neutrality: being intrinsically neither mental nor physical in nature ultimate reality is said to be neutral between the two.