Naturalism is any of several philosophical stances, typically those descended from materialism and pragmatism, that reject the validity of explanations or theories making use of entities inaccessible to natural science, that is, supernatural phenomena: phenomena beyond the natural world that we measure using the scientific method. Naturalism also rejects teleology, or the idea that natural phenomena and events have an innate purpose.
Any method of inquiry or investigation or any procedure for gaining knowledge that limits itself to natural, physical, and material approaches and explanations can be described as naturalist.
Methodological vs. ontological
There is a distinct difference between a methodological assumption of naturalism and an ontological approach. Methodology relates to the accepted procedures. Ontology is a matter of whether something exists. Many philosophers of science only define procedures for investigation to use natural methods for finding natural answers to questions within natural science. Naturalism of this sort says nothing about the existence or nonexistence of the supernatural.
Ontological naturalism is sometimes called "metaphysical naturalism" to distinguish it from the purely functionalist usage of the concept in much of science. Atheism is an example of ontological naturalism. Methodological naturalism implies to most philosophers of science that the endeavor of science is strictly agnostic when it comes to questions of a spiritual or religious nature:
- "Science does not produce evidence against God, Science and religion ask different questions" --Richard Dawkins, biologist and professor of public understanding of science at Oxford University. [1]
It is possible to be a methodological naturalist and an ontological supernaturalist at the same time. While a natural scientist would follow methodological naturalism, they may believe in God (ontological supernaturalism) or they may be an atheist (ontological naturalism).
Naturalism as epistemology
W. V. Quine describes naturalism as the position that there is no higher tribunal for truth than natural science itself. There is no better method than the scientific method for judging the claims of science, and there is neither any need nor any place for a "first philosophy", such as (abstract) metaphysics or epistemology, that could stand behind and justify science or the scientific method.
Therefore philosophy should feel free to make use of the findings of scientists in its own pursuit, while also feeling free to offer criticism when those claims are ungrounded, confused, or inconsistent: philosophy becomes "continuous with" science. Naturalism is not a dogmatic belief that the modern view of science is entirely correct. Instead, it simply holds the processes of the universe have a scientific explanation, the same that modern science is striving to understand.
Naturalism and philosophy of mind
There is currently some dispute over whether naturalism rules out certain areas of philosophy altogether, such as semantics, ethics, aesthetics, or excludes the use of mentalistic vocabulary ("believes," "thinks,") in philosophy of mind. Quine avoided most of these topics, but some recent thinkers have argued that even though (according to them) mentalistic descriptions and value judgements cannot be systematically translated into physicalistic descriptions, they also do not need to presuppose the existence of anything other than physical phenomena.
Donald Davidson, for example, has argued that individual mental states can (must, in fact) be identical with individual brain states, even though a given kind of mental state (belief in Santa Claus) might not be systematically identified with a given kind of brain state (a particular pattern of neural firings): the former weakly "supervenes" upon the latter. The implication is that naturalism can leave non-physical vocabulary intact where the use of that vocabulary can be explained naturalistically; McDowell has dubbed this level of discourse "second nature."
History
The ideas and assumptions of philosophical naturalistism date to the Ionian pre-Socratic philosophers of the 4th century BCE; see, e.g., Jonathan Barnes's introduction to Early Greek Philosophy (Penguin), which describes them as subscribing to principles of empirical investigation that strikingly anticipate naturalism. During the Enlightenment, a number of philosophes including Francis Bacon and Voltaire outlined the philosophical justifications for removing appeal to supernatural forces from investigation of the natural world. Subsequent scientific revolutions would remove much of the remaining theistic baggage from scientific investigation culminating in the development of modern biology and geology which rejected the prevailing origin beliefs of the wider society's religion.
Popular religious criticism of Naturalism
Common popular critics of naturalism are creationists and now the proponents of intelligent design who claim that their religious perspectives are not respected by the current practices and theories of science. These are individuals and organizations who insist that the assumption that the natural world is comprehensible independent of theism or supernatural intervention has caused science to come to incorrect conclusions and has inappropriately excluded research that claims to include such ideas. These groups have been known to argue that the philosophy is necessarily ontological and even a religion itself:
- "It (naturalism) could just as well be called atheism, and is really a religion to be accepted on faith." --Institute for Creation Research[2]
Other creationsts have gone even further and have suggested that the idea is directly responsible for social problems as well. Creationist Benjamin Wiker traces the historical development of the modern materialist perspective starting with the choice of the Epicureans to focus exclusively on the natural realm as a necessary step toward their goals; see his book "Moral Darwinism; How We Became Hedonists".
Because naturalism limits science to investigations without appeal to the supernatural, creationists, such as the Institute for Creation Research and the Creation Science website, claim that it "cannot be justified as a normative principle for all types of science--without doing violence to science as a truth-seeking enterprise" [3].
But supporters of mainstream science defend naturalism saying it is "effective, powerful"[4] "promoting successful investigation"[5] and "an essential aspect of ... the study of the natural universe"[6] They also view the history of science as showing "a progression from supernaturalism to naturalism"[7] Supporters consider the creationist alternative as "positively ineffective and counter-productive, ... in attempts to understand the natural world"[8]