Metaphysical naturalism

Metaphysical naturalism is an approach to metaphysics or ontology, which deals with existence per se. It should not be confused with methodological naturalism, which sees empiricism as the basis for the scientific method.

Regarding science and evolution, Eugenie C. Scott, a notable opponent of teaching creationism or intelligent design in US public schools, stresses the importance of separating metaphysical from methodological naturalism:

If it is important for Americans to learn about science and evolution, decoupling the two forms of naturalism is essential strategy. ... I suggest that scientists can defuse some of the opposition to evolution by first recognizing that the vast majority of Americans are believers, and that most Americans want to retain their faith. It is demonstrable that individuals can retain religious beliefs and still accept evolution as science. Scientists should avoid confusing the methodological naturalism of science with metaphysical naturalism.[6]

— Eugenie C. Scott, "Creationism, Ideology, and Science"

According to metaphysical naturalism, if nature is all there is, just as natural cosmological processes, e.g. quantum fluctuations from a multiverse, lead to the Big Bang,[17] and stellar nucleosynthesis brought upon the earliest chemical elements, the formation of the Solar System and the processes involved in abiogenesis arose from natural causes.[18][19] Naturalists reason about how, not if evolution happened. They maintain that humanity's existence is not by intelligent design but rather a natural process of emergence. With the protoplanetary disk creating planetary bodies, including the Sun and moon, conditions for life to arise billions of years ago, along with the natural formation of plate tectonics, the atmosphere, land masses, and the origin of oceans would also contribute to the kickstarting of biological evolution to occur after the arrival of the earliest organisms, as evidenced through the geological time scale.

Metaphysical naturalists do not believe in a soul or spirit, nor in ghosts, and when explaining what constitutes the mind they rarely appeal to substance dualism. If one's mind, or rather one's identity and existence as a person, is entirely the product of natural processes, three conclusions follow according to W.T. Stace. Evolutionary psychology and neurobiology would be able to provide accounts of how cultural and psychological phenomena, such as religion, morality, emotions, politics, art, and more, evolved through natural processes. Consciousness itself would also be susceptible to the same evolutionary principles that select other traits.[20]

Metaphysical naturalists hold that intelligence is the refinement and improvement of naturally evolved faculties. The certitude of deductive logic remains unexplained by this essentially probabilistic view. Nevertheless, naturalists believe anyone who wishes to have more beliefs that are true than are false should seek to perfect and consistently employ their reason in testing and forming beliefs. Empirical methods (especially those of proven use in the sciences) are unsurpassed for discovering the facts of reality, while methods of pure reason alone can securely discover logical errors.[21]

Naturalism was the foundation of two (Vaisheshika, Nyaya) of the six orthodox schools and one (Carvaka) heterodox school of Hinduism.[22][23] The Carvaka, Nyaya, Vaisheshika schools originated in the 7th, 6th, and 2nd century BCE, respectively.[24]

Western metaphysical naturalism originated in ancient Greek philosophy. The earliest pre-Socratic philosophers, especially the Milesians (Thales, Anaximander, and Anaximenes) and the atomists (Leucippus and Democritus), were labeled by their peers and successors "the physikoi" (from the Greek φυσικός or physikos, meaning "natural philosopher," borrowing on the word φύσις or physis, meaning "nature") because they investigated natural causes, often excluding any role for gods in the creation or operation of the world. This eventually led to fully developed systems such as Epicureanism, which sought to explain everything that exists as the product of atoms falling and swerving in a void.[25]

Aristotle surveyed the thought of his predecessors and conceived of nature in a way that charted a middle course between their excesses.[26]

Plato's world of eternal and unchanging Forms, imperfectly represented in matter by a divine Artisan, contrasts sharply with the various mechanistic Weltanschauungen, of which atomism was, by the fourth century at least, the most prominent… This debate was to persist throughout the ancient world. Atomistic mechanism got a shot in the arm from Epicurus… while the Stoics adopted a divine teleology… The choice seems simple: either show how a structured, regular world could arise out of undirected processes, or inject intelligence into the system. This was how Aristotle… when still a young acolyte of Plato, saw matters. Cicero… preserves Aristotle's own cave-image: if troglodytes were brought on a sudden into the upper world, they would immediately suppose it to have been intelligently arranged. But Aristotle grew to abandon this view; although he believes in a divine being, the Prime Mover is not the efficient cause of action in the Universe, and plays no part in constructing or arranging it... But, although he rejects the divine Artificer, Aristotle does not resort to a pure mechanism of random forces. Instead he seeks to find a middle way between the two positions, one which relies heavily on the notion of Nature, or phusis.[27]

With the rise and dominance of Christianity in the West and the later spread of Islam, metaphysical naturalism was generally abandoned by intellectuals. Thus, there is little evidence for it in medieval philosophy. The reintroduction of Aristotle's empirical epistemology as well as previously lost treatises by Greco-Roman natural philosophers which was begun by the medieval Scholastics without resulting in any noticeable increase in commitment to naturalism.

It was not until the early modern era of philosophy and the Age of Enlightenment that naturalists like Benedict Spinoza (who put forward a theory of psychophysical parallelism), David Hume,[28] and the proponents of French materialism (notably Denis Diderot, Julien La Mettrie, and Baron d'Holbach) started to emerge again in the 17th and 18th centuries. In this period, some metaphysical naturalists adhered to a distinct doctrine, materialism, which became the dominant category of metaphysical naturalism widely defended until the end of the 19th century.

Immanuel Kant rejected (reductionist) materialist positions in metaphysics,[29] but he was not hostile to naturalism. His transcendental philosophy is considered to be a form of liberal naturalism.[30]

In late modern philosophy, Naturphilosophie, a form of natural philosophy, was developed by Friedrich Wilhelm Joseph von Schelling[31] and Georg Wilhelm Friedrich Hegel[31] as an attempt to comprehend nature in its totality and to outline its general theoretical structure.

A version of naturalism that arose after Hegel was Ludwig Feuerbach's anthropological materialism,[32] which influenced Karl Marx and Friedrich Engels's historical materialism, Engels's "materialist dialectic" philosophy of nature (Dialectics of Nature), and their follower Georgi Plekhanov's dialectical materialism.[33]

Another notable school of late modern philosophy advocating naturalism was German materialism: members included Ludwig Büchner, Jacob Moleschott, and Carl Vogt.[34][35]

In the early 20th century, matter was found to be a form of energy and therefore not fundamental as materialists had assumed. (See History of physics.) In contemporary analytic philosophy, renewed attention to the problem of universals, philosophy of mathematics, the development of mathematical logic, and the post-positivist revival of metaphysics and the philosophy of religion, initially by way of Wittgensteinian linguistic philosophy, further called the naturalistic paradigm into question. Developments such as these, along with those within science and the philosophy of science brought new advancements and revisions of naturalistic doctrines by naturalistic philosophers into metaphysics, ethics, the philosophy of language, the philosophy of mind, epistemology, etc., the products of which include physicalism and eliminative materialism, supervenience, causal theories of reference, anomalous monism, naturalized epistemology (e.g. reliabilism), internalism and externalism, ethical naturalism, and property dualism, for example.

A politicized version of naturalism that has arisen in contemporary philosophy is Ayn Rand's Objectivism. Objectivism is an expression of capitalist ethical idealism within a naturalistic framework.

The current usage of the term naturalism "derives from debates in America in the first half of the last century. The self-proclaimed 'naturalists' from that period included John Dewey, Ernest Nagel, Sidney Hook and Roy Wood Sellars."[36]

Currently, metaphysical naturalism is more widely embraced than in previous centuries, especially but not exclusively in the natural sciences and the Anglo-American, analytic philosophical communities. While the vast majority of the population of the world remains firmly committed to non-naturalistic worldviews, prominent contemporary defenders of naturalism and/or naturalistic theses and doctrines today include J. J. C. Smart, David Malet Armstrong, David Papineau, Paul Kurtz, Brian Leiter, Daniel Dennett, Michael Devitt, Fred Dretske, Paul and Patricia Churchland, Mario Bunge, Jonathan Schaffer, Hilary Kornblith, Quentin Smith, Paul Draper and Michael Martin, among many other academic philosophers.

According to David Papineau, contemporary naturalism is a consequence of the build-up of scientific evidence during the twentieth century for the "causal closure of the physical", the doctrine that all physical effects can be accounted for by physical causes.[37]

By the middle of the twentieth century, the acceptance of the causal closure of the physical realm led to even stronger naturalist views. The causal closure thesis implies that any mental and biological causes must themselves be physically constituted, if they are to produce physical effects. It thus gives rise to a particularly strong form of ontological naturalism, namely the physicalist doctrine that any state that has physical effects must itself be physical.

From the 1950s onwards, philosophers began to formulate arguments for ontological physicalism. Some of these arguments appealed explicitly to the causal closure of the physical realm (Feigl 1958, Oppenheim and Putnam 1958). In other cases, the reliance on causal closure lay below the surface. However, it is not hard to see that even in these latter cases the causal closure thesis played a crucial role.[38]

— David Papineau, "Naturalism" in the Stanford Encyclopedia of Philosophy

According to Steven Schafersman, president of Texas Citizens for Science, an advocacy group opposing creationism in public schools,[39] the progressive adoption of methodological naturalism—and later of metaphysical naturalism—followed the advances of science and the increase of its explanatory power.[40] These advances also caused the diffusion of positions associated with metaphysical naturalism, such as existentialism.[41]

In contemporary continental philosophy, Quentin Meillassoux proposed speculative materialism, a post-Kantian return to David Hume which can strengthen classical materialist ideas.[42]

In the context of creation and evolution debates, Internet Infidels co-founder Jeffery Jay Lowder argues against what he calls "the argument from bias", that a priori, the supernatural is merely ruled out due to an unexamined stipulation. Lowder believes "there are good empirical reasons for believing that metaphysical naturalism is true, and therefore a denial of the supernatural need not be based upon an a priori assumption".[43]

Several metaphysical naturalists have used the trends in scientific discoveries about minds to argue that no supernatural minds exist. Jeffery Jay Lowder says, "Since all known mental activity has a physical basis, there are probably no disembodied minds. But God is conceived of as a disembodied mind. Therefore, God probably does not exist."[44] Lowder argues the correlation between mind and brain implies that supernatural souls do not exist because the theist position, according to Lowder, is that the mind depends upon this soul instead of the brain.[43]

In contrast with the argument from reason or evolutionary argument against naturalism, it can be argued that cognitive biases are better explained by natural causes than as the work of God.[45]

Philosophers and scientists such as Victor Reppert, William Hasker, and Alvin Plantinga have developed an argument for dualism dubbed the "argument from reason." They credit C.S. Lewis with first bringing the argument to light in his book Miracles; Lewis called the argument "The Cardinal Difficulty of Naturalism," which was the title of chapter three of Miracles.[46]

The argument postulates that if, as naturalism entails, all of our thoughts are the effect of a physical cause, then we have no reason for assuming that they are also the consequent of a reasonable ground. However, knowledge is apprehended by reasoning from ground to consequent. Therefore, if naturalism were true, there would be no way of knowing it (or anything else), except by a fluke.[46]

Through this logic, the statement "I have reason to believe naturalism is valid" is inconsistent in the same manner as "I never tell the truth."[47] That is, to conclude its truth would eliminate the grounds from which it reaches it. To summarize the argument in the book, Lewis quotes J. B. S. Haldane, who appeals to a similar line of reasoning:[48]

If my mental processes are determined wholly by the motions of atoms in my brain, I have no reason to suppose that my beliefs are true ... and hence I have no reason for supposing my brain to be composed of atoms.

— J. B. S. Haldane, Possible Worlds, page 209

In his essay "Is Theology Poetry?," Lewis himself summarises the argument in a similar fashion when he writes:

If minds are wholly dependent on brains, and brains on biochemistry, and biochemistry (in the long run) on the meaningless flux of the atoms, I cannot understand how the thought of those minds should have any more significance than the sound of the wind in the trees.

— C. S. Lewis, The Weight of Glory and Other Addresses, page 139

But Lewis later agreed with Elizabeth Anscombe's response to his Miracles argument.[49] She showed that an argument could be valid and ground-consequent even if its propositions were generated via physical cause and effect by non-rational factors.[50] Similar to Anscombe, Richard Carrier and John Beversluis have written extensive objections to the argument from reason on the untenability of its first postulate.[51]

Notre Dame philosophy of religion professor and Christian apologist Alvin Plantinga argues, in his evolutionary argument against naturalism, that the probability that evolution has produced humans with reliable true beliefs, is low or inscrutable, unless their evolution was guided, for example, by God. According to David Kahan of the University of Glasgow, in order to understand how beliefs are warranted, a justification must be found in the context of supernatural theism, as in Plantinga's epistemology.[52][53][54] (See also supernormal stimuli).

Plantinga argues that together, naturalism and evolution provide an insurmountable "defeater for the belief that our cognitive faculties are reliable", i.e., a skeptical argument along the lines of Descartes' evil demon or brain in a vat.[55]

Take philosophical naturalism to be the belief that there aren't any supernatural entities—no such person as God, for example, but also no other supernatural entities, and nothing at all like God. My claim was that naturalism and contemporary evolutionary theory are at serious odds with one another—and this despite the fact that the latter is ordinarily thought to be one of the main pillars supporting the edifice of the former. (Of course I am not attacking the theory of evolution, or anything in that neighborhood; I am instead attacking the conjunction of naturalism with the view that human beings have evolved in that way. I see no similar problems with the conjunction of theism and the idea that human beings have evolved in the way contemporary evolutionary science suggests.) More particularly, I argued that the conjunction of naturalism with the belief that we human beings have evolved in conformity with current evolutionary doctrine... is in a certain interesting way self-defeating or self-referentially incoherent.[55]

— Alvin Plantinga, "Introduction" in Naturalism Defeated?: Essays on Plantinga's Evolutionary Argument Against Naturalism

Branden Fitelson of the University of California, Berkeley and Elliott Sober of the University of Wisconsin–Madison argue that Plantinga must show that the combination of evolution and naturalism also defeats the more modest claim that "at least a non-negligible minority of our beliefs are true", and that defects such as cognitive bias are nonetheless consistent with being made in the image of a rational God. Whereas evolutionary science already acknowledges that cognitive processes are unreliable, including the fallibility of the scientific enterprise itself, Plantinga's hyperbolic doubt is no more a defeater for naturalism than it is for theistic metaphysics founded upon a non-deceiving God who designed the human mind: "[neither] can construct a non-question-begging argument that refutes global skepticism."[56] Plantinga's argument has also been criticized by philosopher Daniel Dennett and independent scholar Richard Carrier who argue that a cognitive apparatus for truth-finding can result from natural selection.[57]

Edward Feser, in his 2008 book The Last Superstition: A Refutation of the New Atheism, lays a plenary case against naturalism by re-examining pre-Modern philosophy. Beginning in the second chapter, Feser cites the Platonic[58] and Aristotelian[59] answers to the problem of universals—that is, realism. Feser also offers arguments against nominalism.[60] And by defending realism and rejecting nominalism, he rejects eliminative materialism—and thus naturalism.

In the third chapter, Feser summarizes three of Thomas Aquinas's arguments for the existence of God.[61] These include arguments for an unmoved mover,[62] first, uncaused cause[63] and (supernatural) supreme intelligence,[64] concluding that these must exist not as a matter of probability—as in the intelligent design view, particularly of irreducible complexity[65]—but as a necessary consequence of "obvious, though empirical, starting points".[66]

• Edward B. Davis and Robin Collins, "Scientific Naturalism." In Science and Religion: A Historical Introduction, ed. Gary B. Ferngren, Johns Hopkins University Press, 2002, pp. 322–34.

• Gary Drescher, Good and Real, The MIT Press, 2006. ISBN 0-262-04233-9
• David Malet Armstrong, A World of States of Affairs, Cambridge: Cambridge University Press, 1997. ISBN 0-521-58064-1
• Mario Bunge, 2006, Chasing Reality: Strife over Realism, University of Toronto Press. ISBN 0-8020-9075-3 and 2001, Scientific Realism: Selected Essays of Mario Bunge, Prometheus Books. ISBN 1-57392-892-5
• Richard Carrier, 2005, Sense and Goodness without God: A Defense of Metaphysical Naturalism, AuthorHouse. ISBN 1-4208-0293-3
• Mario De Caro & David Macarthur (eds), 2004. Naturalism in Question. Cambridge, Mass: Harvard University Press. ISBN 0-674-01295-X
• Daniel Dennett, 2003, Freedom Evolves, Penguin. ISBN 0-14-200384-0 and 2006
• Andrew Melnyk, 2003, A Physicalist Manifesto: Thoroughly Modern Materialism, Cambridge University Press. ISBN 0-521-82711-6
• Jeffrey Poland, 1994, Physicalism: The Philosophical Foundations, Oxford University Press. ISBN 0-19-824980-2

• James Beilby, ed., 2002, Naturalism Defeated? Essays on Plantinga's Evolutionary Argument Against Naturalism, Cornell University Press. ISBN 0-8014-8763-3
• William Lane Craig and J.P. Moreland, eds., 2000, Naturalism: A Critical Analysis, Routledge. ISBN 0-415-23524-3
• Stewart Goetz and Charles Taliaferro, 2008, Naturalism, Eerdmans Publishing. ISBN 978-0-8028-0768-7
• Phillip E. Johnson, 1998, Reason in the Balance: The Case Against Naturalism in Science, Law & Education, InterVarsity Press. ISBN 0-8308-1929-0 and 2002, The Wedge of Truth: Splitting the Foundations of Naturalism, InterVarsity Press. ISBN 0-8308-2395-6
• C.S. Lewis, ed., 1996, "Miracles", Harper Collins. ISBN 0-06-065301-9
• Michael Rea, 2004, World without Design: The Ontological Consequences of Naturalism, Oxford University Press. ISBN 0-19-924761-7
• Victor Reppert, 2003, C.S. Lewis's Dangerous Idea: In Defense of the Argument from Reason, InterVarsity Press. ISBN 0-8308-2732-3
• Mark Steiner, 2002, The Applicability of Mathematics as a Philosophical Problem, Harvard University Press. ISBN 0-674-00970-3