As most commonly understood in philosophy, the term denotes the doctrine that whatever exists is either matter, or entirely dependent on matter in its existence. The precise meaning and status of this doctrine are, however, far from clear.
What are the properties of that matter in the relevant sense must, could, or could not possess ? Is matter to be regarded simply as that which is extended in both space and time ? Or if not, what further properties are essential to it ? Is there a relevant distinction to be drawn here between existence or occurence and being, and reality ? And how exactly are the space and time in which matter extends, the forces moving it, and the consciousness perceiving it, dependent on it ?
The range of possible anwsers makes materialism in effect a somewhat ill-defined group of doctrines rather than one specific thesis.
Further, even supposing the content of the doctrine is sufficiently clarified, why should it be accepted ? There are certainly no observational or analytical methods it as true.
Forms of materialism appear in the history of thought as far back at least as Democritus and Epicurus, who attempted to describe natural processes and human experience in terms of arrangements and rearrangements of changeless atoms, or indivisibles material particles, in empty space. Despite inevitable religious opposition there have been various revivals of such ideas, beginning in the 17th century in cunjunction with the new physics of Galileo, and later, Nexton.
Hobbes produced a drastic and brilliant account of such materialism and the promise of an all-explaining scientific world-view was pursued, by, for example, Holbach and La Mettrie.
Recently, marxist thinkers have replaced such mechanistic materialism by their dialectical materialism, containing contradictions which procide the motive force for change.