Three metaphysical views have dominated western philosophical thinking: dualism, idealism, and physicalism. Dualism, as explained by Descartes holds that mind and matter are two different and distinct types of substances. Idealism and physicalism are both forms of monism. Idealism, exemplified by the work of Bishop George Berkeley, and implied by the work of David Hume, holds that we are not justified in believing in anything but mental qualities and minds. Accordingly, the notion of physical things apart from mental qualities is best dispensed with. Most scientists today are physicalists. This view holds that all things are physical. According to physicalism, all mental phenomena are caused by a physical brain. Physicalism is a form of reductionism that reduces all mental phenomena to physical explanations. All of three of these views have their shortcomings.
Two similar and promising metaphysical views have been developed to address the shortcomings of the main three metaphysical views of the west. These are the views of process philosophy and the metaphysics of quality. Process philosophy builds upon the work of Alfred North Whitehead. The metaphysics of quality is an independent view developed by Robert Pirsig.