Accusations of materialism in science tend to confuse two differing meanings of the word:
Ontological materialism is the belief, or assumption, that only material matter and energy exist. For the ontological materialist anything immaterial must be the product of the material. In principle all immaterial phenomena must be reducible to (explicable by) natural laws.
Methodological materialism is neither a belief nor an assumption but a restriction on method. Briefly stated it holds that a non-material assumption is not to be made. Science, for example, is necessarily methodologically materialist. Science wishes to describe and explain nature. Diversion into the “supernatural” begins to describe and explain matters that are not natural and obfuscate the natural.
Methodological materialism is a defining characteristic of science in the same way that “methodological woodism” is a defining characteristic of carpentry. Science seeks to construct natural explanations for natural phenomena in the same way that carpentry seeks to construct objects out of wood. In operating in this manner neither discipline denies the existence of supernatural forces or sheet plastics, their usefulness or validity. The use of either supernatural forces or sheet plastics is simply distinguished as belonging to separate disciplines.
Many scientists are also ontological materialists. Richard Dawkins espouses ontological materialism when he claims a completeness of science.
Both forms of materialism are very closely related to philosophical and methodological naturalism and at first glance seem almost identical. Materialism and naturalism differ...