Metaphysical or ontological naturalism is any worldview in which the world is amenable to a unified study that includes the natural sciences and in this sense the world is a unity. According to such a view, nature is all there is, and all things supernatural (which stipulatively includes spirits and souls and non-natural values) do not exist, or they are reducible to natural things. It is often simply referred to as naturalism, and occasionally as philosophical naturalism or ontological naturalism, though all those terms have other meanings as well, with naturalism often referring to methodological naturalism.
This particular definition rests in an ambiguity caused by the use of the term "supernatural" by Richard Carrier and other apologists for naturalism whereby this word indicates non-materially reducible entities (spiritual substances) rather than the traditional meaning (where a spiritual substance, if created, is encompassed within the natural world, though being a spiritual or immaterial substance).
A metaphysical naturalist begins by examining their epistemology. Constructing one in a reasonable and thoughtful way requires an examination of what is being investigated, how to discover if it is a possibility, and spending the time necessary to reach conclusions.
In practice, however, one's epistemology is usually only superficially examined and applied merely by intuition. More often, one’s epistemology is simply borrowed from one's parents, teachers, or peers and not examined or constructed by the individual. If one has not even thought about it, much less carefully examined and tested what one thinks one knows, it's unlikely that one's unexamined assumptions will just by pure chance be sound and trustworthy. Everything one does, believes, and desires ultimately depends upon one's knowledge being correct.
Therefore it is the metaphysical naturalist’s duty is to question all things and have a well-grounded faith in what is well-investigated and well-proved, rather than what is merely well-asserted or well-liked.
There are many different varieties of metaphysical naturalism, but all can be separated into two general categories, physicalism and pluralism. Physicalism entails the claim that everything everyone has observed or claimed to observe is actually the product of fundamentally mindless arrangements or interactions of matter-energy in space-time, and therefore it is unreasonable to believe anything else exists. Pluralism (which includes dualism) adds to this the existence of fundamentally mindless things besides matter-energy in space-time (such as reified abstract objects).
What all metaphysical naturalists agree on, however, is that the fundamental constituents of reality, from which everything derives and upon which everything depends, are fundamentally mindless. So if any variety of metaphysical naturalism is true, then any mental properties that exist (hence any mental powers or beings) are causally derived from, and ontologically dependent on, systems of nonmental properties, powers, or things. This means metaphysical naturalism would be false if any distinctly mental property, power, or entity exists that is not ontologically dependent on some arrangement of nonmental things, or that is not causally derived from some arrangement of nonmental things, or that has causal effects without the involvement of any arrangement of nonmental things that is already causally sufficient to produce that effect.
In lay terms, if metaphysical naturalism is true, then all minds, and all the contents and powers and effects of minds, are entirely constructed from or caused by natural phenomena. If metaphysical naturalism is false, then some minds, or some of the contents or powers or effects of minds, are causally independent of nature (either they partly or wholly cause themselves, or they exist or operate fundamentally on their own).
Belief in the latter entails some form of supernaturalism (the opposite of naturalism), which is not limited to supernatural beings, but can encompass mindless things with distinctly mental properties, like magical objects (see magic and incantation) or causally efficacious Platonic forms or the existence of love as a cosmic force.
The relationship between metaphysical and methodological naturalism is not one-dimensional and varies among individual thinkers. To understand this relationship, two varieties of methodological naturalism should be distinguished. Absolute methodological naturalism is the view that it is in some sense impossible for any empirical method to discover supernatural facts, even if there are some. [This is compatible with (but does not entail) the view that something other than empirical methods might be able to discover supernatural facts.] Contingent methodological naturalism entails the belief that, judging from past experience, empirical methods are far more likely to uncover natural facts than supernatural ones. It is generally an ill-advised waste of resources to pursue supernatural hypotheses, but it would not be impossible to confirm them empirically if any were true. Thus not all methodological naturalists will be metaphysical naturalists.
Metaphysical naturalism is most commonly distinguished from methodological naturalism that refers to the long-standing convention in science of the scientific method making the assumption that observable events in nature are explained only by natural causes. Methodological naturalism entails the belief that for one reason or another empirical methods will only ascertain natural facts. The supernatural is not explicitly denied, but supernatural explanations are considered outside of science.
Humanity's existence as conscious animals of superior intelligence and sagacity, is explained not as the outcome of intelligent design nor as a mere accidental combination of chemicals (such as originated life), but as the product of a dynamic, random system that generates highly complex order on its own, without any guidance. Since this entails that the properties of living organisms have been randomly derived solely according to their differential reproductive success, naturalists interpret cells, organs, and species as having a "purpose" or "function" in terms of their ability to increase differential reproductive success, but do not perceive in this any moral goal that should be emulated or furthered, since nature is the cause, and nature has no compassion or plan. However, this does not exclude the possibility of true moral propositions derived from evolved facts (see Value of society and Primacy of happiness below).
There is nothing of any greater value than human happiness. Therefore, all conduct and behavior should be oriented toward that aim, maximizing its availability while minimizing opposing risks. Though happiness is an accidental product of naturally and culturally evolved attributes of the human animal, it exceeds everything else in human experience in terms of its enjoyability and desirability, and therefore it is self-contradictory to assert that there is anything humans would enjoy or want more than their own happiness. However, there are tangible differences between happiness in this sense (as a form of pleasant contentment that everyone would desire more than anything else) and mere pleasure, as also between physical and intellectual pleasure. There are also complex realities involved in pursuing happiness, most notably those created by the complexities and limitations of natural human psychology and the complexities and limitations of living within (and depending upon) a social system. When all these distinctions and complexities are understood, a system of behavioral or attitudinal principles can be deduced, which is what naturalists define as morality. It is probably a universal conclusion among naturalists that this analysis ultimately produces a commitment to the Golden Rule, with many contemporary naturalists further concluding that by cultivating the personal virtues of compassion and honesty we most effectively realize this Rule and, as a result, most effectively increase our access to happiness (in frequency, degree, duration, and probability).
Metaphysical naturalism appears to have originated in early Greek philosophy. The earliest presocratic philosophers, such as Thales, Anaxagoras or most especially 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 sought to explain everything by reference to natural causes alone, often distinctly excluding any role for gods, spirits or magic 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 moving in a void, or the advanced Aristotelianism of Strato of Lampsacus, which sought to explain everything that exists as the inevitable outcome of uncreated natural forces or tendencies.
In their definition of nature, the ancient Greeks distinguished "nature" from "artifice." Anything that resulted from the innate properties of a thing was regarded as having a natural cause, regardless of whether those properties themselves were intelligently arranged or not, while anything that resulted from intelligent action was regarded as having an artificial cause, regardless of whether the intelligence itself was the product of natural causes. Thus, natural causes were partially distinguished from intelligent causes. It was often assumed that some intelligent causes were primary causes and not solely the product of natural properties, but not everyone agreed. Following the physikoi and their successors, some ancient intellectuals denied the existence of any intelligent causes that were not entirely the product of natural causes (thus reducing all intelligent causes to natural causes), and they represent the earliest metaphysical naturalists. However, only a few Greek and Roman intellectuals embraced such a view, though of those few, Epicurus and Strato of Lampsacus were the most famous.
Metaphysical naturalism is most notably a Western phenomenon, but an equivalent idea has long existed in the East. Though unnamed and never articulated into a coherent system, one tradition within Confucian philosophy embraced a view that can correctly be called metaphysical naturalism, dating back at least to Wang Chong in the 1st century, if not earlier. But this tradition arose independently and had little influence on the development of modern naturalist philosophy or on Eastern or Western culture.
With the rise and dominance of Christianity and the decline of secular philosophy in the West, metaphysical naturalism became heretical and eventually illegal, thus making it difficult to document the history of metaphysical naturalism in the Middle Ages. When the Renaissance reintroduced numerous lost treatises by Greek and Roman natural philosophers, many of the ideas and concepts of naturalism were picked up again, contributing to a new Scientific Revolution that would greatly advance the study and understanding of nature. But social and legal hostility continued to prevent advocates of metaphysical naturalism from coming forward, if there were any, until the political advances of the Age of Enlightenment made genuine free speech possible. Then a few intellectuals publicly renewed the case for metaphysical naturalism, like Baron d'Holbach in the 18th century.
In this period, metaphysical naturalism finally acquired a distinct name, materialism, which became the only category of metaphysical naturalism widely defended until the 20th century, when advances in physics as well as philosophy made the original premise of materialism untenable. In physics, matter was found to be a form of energy and therefore not the fundamental constituent of reality as materialists had been presuming. In philosophy, renewed attention to the problem of universals and other undeniable but "immaterial" realities further called materialism into question. These developments refined naturalism into the two forms now widely advanced (physicalism and naturalist pluralism, as explained above), both corresponding more closely to the system historians believe was articulated by Strato, rather than the system advanced by Epicurus as is commonly thought.
Currently, metaphysical naturalism is more widely embraced than ever before, especially but not exclusively in the scientific community, where acquaintance with the facts of nature is broader and more secure, though metaphysical naturalism is still a minority worldview. The vast majority of the population of the world remains firmly committed to supernaturalist worldviews. However, it is likely that a substantial minority or even a majority of the population in certain European and other first world countries might embrace metaphysical naturalism in some basic, unarticulated sense. To date, nothing that is not physical has ever been discovered, and so metaphysical naturalism remains a valid position based upon what is currently known. Today, noteworthy proponents are too numerous to count, but prominent defenders of metaphysical naturalism as a complete worldview include Mario Bunge, Richard Carrier, Richard Dawkins, Daniel Dennett, Sam Harris, and David Mills.
As a final note to the history of metaphysical naturalism, certain extreme varieties of politicized naturalism have arisen in the West, most notably Marxism in the 19th century and Objectivism in the 20th century. Marxism is an expression of communist or socialist ideals in a naturalist framework, while Objectivism is the exact opposite, an expression of capitalist ideals in a naturalist framework. However, today most advocates of metaphysical naturalism in first world countries reject both extremes and embrace the more moderate political ideals of secular humanism.
There are many arguments for belief in metaphysical naturalism. Only a few will be surveyed here, and only in brief. There are many others, but most involve refinements, variants or sub-arguments to the following.
For over three hundred years empirical methods have consistently discovered only natural things and causes, even underlying many things once thought to be supernatural. Meanwhile, no other methods have produced any consistent conclusions about the substance or causes of anything, much less anything supernatural. The logical inference is that since countless past gaps in knowledge have been filled by naturalism, and by nothing else, probably all remaining gaps in knowledge will be filled by naturalism as well. This simply extends a principle fundamental to science as a whole, that we should presume any new phenomenon obeys known laws of physics until we have empirically proven otherwise. Hence we should presume that any unexplained fact has a natural explanation until we have empirically proven otherwise. Therefore, since we have not found empirical proof of anything supernatural, and since we have abundant reason from past precedent to expect that natural explanations underlie everything, metaphysical naturalism is most probably true.
Some naturalists argue that sound naturalist hypotheses about facts still scientifically unexplained outperform all other hypotheses in explanatory scope and power, relative to explanatory simplicity. If that's true, then metaphysical naturalism is the best explanation of everything we observe and experience, and is therefore probably true. This amounts to arguing that everything makes more sense if naturalism is true, many details about ourselves and the world are more probable if naturalism is true, and to explain even the most mysterious of facts naturalism has to resort to fewer ad hoc assumptions than any known alternative. For example, resorting to the supernatural as explanation typically requires an array of completely ad hoc assumptions about the abilities, nature, limitations, and desires of supernatural forces. Even so, much of what remains unexplained is then elucidated as simply the "mystery" of the enigmatic will of the supernatural or as beyond human ken. Naturalism, on the other hand, relies much more heavily on assumptions already scientifically established as precedents and principles, and makes more specific predictions about what the observed results would be if naturalism were true, which align very well with actual observations.
One major way in which naturalism explains things better than alternatives is that if the supernatural exists (whether as gods, powers, or spirits), it is so silent and inert that its effects are almost never observed, despite vast and extensive searching. Even the relatively few alleged observations take place only under dubious conditions lacking in sound empirical controls or tests, and on those occasions when they are subsequently subjected to sound controls or tests, they turn out to be false. Our inability to uncover clear evidence of anything supernatural is somewhat improbable if anything supernatural exists, but very probable if nothing supernatural exists, and therefore metaphysical naturalism is probably true.
Scientists have accumulated vast evidence that the human mind is a product of a functioning brain, which is entirely constructed from different interacting physical systems that evolved over time through the animal kingdom, and that our brain is now the most complex machine found anywhere in nature, and that our minds appear limited to our brain's physical needs and capabilities. We have discovered no clear evidence of any other kind of mind, nor any clear evidence that our minds can exceed the limitations of our physical brain, nor any clear evidence that our brains did not slowly evolve through billions of years of natural selection. This is the only way we would observe the facts to be if naturalism were true (since there is no other way to have a mind on naturalism except as the product of a slowly evolved, highly complex physical system like our brain), but if supernaturalism were true (and therefore some minds or mental content exist independently of a physical machine like our brain), what we observe is not the only way things could be (since by now we could have and likely would have observed some supernatural elements of our or other minds or observed mental powers in other things). Since this observation is less probable if supernaturalism is true, metaphysical naturalism is more likely to be true.
If naturalism is true, then the formation of intelligent life via natural processes in any one given small corner of a young universe is unlikely. Therefore, the only way we would be observing life to exist if naturalism were true, is if the universe were so immensely old and big that events of such an improbability will be very rare but still likely to occur. We observe the universe to be that immensely old and big and life to be that rare. In addition, the universe is almost entirely lethal to life. By far most of what exists is a deadly radiation-filled vacuum, and by far most matter in the cosmos composes lethal environments like stars and black holes. Insofar as supernaturalism allows other possible arrangements for us to observe, such as universes more universally hospitable to life, universes far too young or small to produce life by mechanical accident, or universes in which life is far more common, what we observe to be the case is less probable given supernaturalism than given naturalism, and therefore metaphysical naturalism is more probably true.
Finally, joining the first two arguments to the rest, we have an argument from implausibility. The only supernatural hypothesis that does not fall to any of the above arguments is a hypothesis wherein the proposed supernatural entity or ability is so rare, so obscure, so inert, so unrelated to human experience, and so strange and complex as to entail exactly the same observations already entailed by naturalism, that there is no reasonable argument to be made for believing it. Occam's razor is invoked - In the absence of any reasonable argument to believe anything supernatural exists or explains anything, and in the presence of some reasonable arguments to believe the natural world exists and explains everything, metaphysical naturalism should be accepted until disproved.
In much the same way that theology consists largely of working out which theories of divinity are plausible and coherent (and which are not), so naturalist philosophy consists largely of working out which naturalist worldviews are plausible and coherent (and which are not). Consequently, attacking inept constructions of naturalism or caricatures of naturalism is akin to attacking inept theologies or caricatures of theology. Just as critics of the existence of God need to address the most carefully constructed and best defended theologies, critics of naturalism need to address the most carefully constructed and best defended naturalist worldviews.
That said, metaphysical naturalism has no lack of critics. It has been loathed by countless defenders of supernatural worldviews for thousands of years and has been subject to countless attacks. Some arguments present significant challenges to naturalist philosophy. Those arguments will be briefly surveyed here.
The most commonly voiced argument against naturalism is that it leads to human despair, though this argument does not address the truth value of naturalism. There are many forms of this argument. Some emphasize the fact that naturalism entails there is no cosmic meaning of life, others propose that a religion promising eternal salvation is a safer bet (as in Pascal's Wager), while others claim naturalism entails the elimination of free will, which allegedly entails there is no knowledge, hope or moral responsibility. This is an example of an Appeal to consequences.
Many people claim to have seen, felt, or talked to God or any number of other spirits, and claim these religious experiences refute naturalism. It is important to note that this argument does not conflict with some naturalistic beliefs which claim that what is commonly called supernatural is, in fact, part of the natural world. Proponents of other branches of naturalism dispute the validity of the experiences offered as proof for this argument.
Often some miracle is offered as evidence refuting naturalism, including alleged cases of supernatural healing, fulfilled prophetic or psychic predictions, or the supposed impossibility of composing some book (like the Bible or the Koran) without divine aid. Naturalists often doubt the validity of these miracles.
One of the more esoteric arguments against naturalism is to claim that it is in some sense impossible for the universe to exist unless it is caused or cohabited by a supernatural entity. There are several forms of this argument, some requiring a demonstration of the premise that the universe began to exist (like the Kalam cosmological argument). Others argue that even if the universe has always existed, the act of getting from some distant point in the past to now would involve transcending an infinite amount of time through consecutive addition, an arguably impossible feat. As the impossible has allegedly been demonstrated as having occurred, the opponent of naturalism suggests the necessity of supernatural activity.
Also known as the Fine Tuning argument, this is the claim that the fundamental constants of physics and laws of nature appear so finely-tuned to permit life that only a supernatural engineer can explain it.
Many claim the origin of life was too improbable to have occurred without supernatural intervention and therefore naturalism fails to explain the appearance of life. This argument is usually based on statistics and figures that supposedly tell the probability of life occurring through natural means. It is argued that this probability is so small as to be safely assumed to be zero.
Recently popular is the legally unscientific claim that certain structures in evolved organisms are too complex to have evolved by natural selection and can only be explained as the result of intelligent design. This argument suggests that certain biological instances (the favorite example being the eye) could not have occurred gradually, but must have come to be instantaneously. This is referred to as the argument from irreducible complexity.
Since no one has yet scientifically explained the qualitative nature of conscious experience, otherwise known as qualia, some argue that naturalism is therefore refuted or should not be believed. Proponents of this argument suggest that naturalism's lack of a definite explanation on this matter is not a result of a simple lack of research (which would indicate that science may one day explain qualia), but that naturalism cannot explain qualia because no valid physical explanation exists.
Some have argued that certain features of human reason cannot be explained by naturalism. For example, it is claimed that naturalism cannot explain intentionality, mental causation, or the existence of logical laws or abstract objects.
Some claim naturalism cannot explain the existence of physical laws. This argument takes many forms, but the two most common are the claim that the mathematical nature of physical laws entails a supernatural mind behind them and the claim that naturalism can provide no ontological foundation for physical laws, requiring some supernatural power or being to realize and maintain them. Yet another argument, related to the argument from incoherence, states that because all data available to naturalists is based on physical laws, any attempt on the part of naturalism to explain physical laws would be an instance of begging the question.
Sometimes it is claimed that naturalism entails self-contradictory commitments. This argument involves the claim that metaphysical naturalism precludes all nonphysical data in its premise. Because metaphysical naturalism assumes that everything is physical, using physical data in support of it would constitute circular reasoning. At this point in the argument, the only data that could plausibly support metaphysical naturalism would be nonphysical data. Opponents then argue that any existence of such data would be a direct contradiction of metaphysical naturalism. Finally, it is concluded that metaphysical naturalism is an illogical worldview.
There are two kinds of moral argument: the claim that naturalism eliminates morality and the claim that moral facts exist that naturalism cannot explain. The first claim, that there can be no moral truth if naturalism is true, is a variety of the argument from despair already noted above, and naturalists respond in the same way here as there. In addition, naturalists argue we can derive moral propositions from actual facts about human needs and desires and the social and physical environment we inhabit. As to the second claim, naturalists respond that no one has ever demonstrated the actual existence of any moral facts that naturalism cannot explain.
Alvin Plantinga, a contemporary philosopher of epistemology at Notre Dame has argued that anyone who holds to the truth of both metaphysical naturalism and evolution is irrational in doing so. His argument relies on establishing that the probability that unguided evolution would have produced reliable cognitive faculties is either low or inscrutable. If so, one who holds both naturalism and evolution acquires a “defeater” for every belief he holds, including the beliefs associated with naturalism and evolution.
From intelligent design to quantum divine action--recent accounts of God and nature.(Intelligent Design: William A. Dembski & Michael Ruse in Dialogue)(Book review)
Jun 01, 2008; INTELLIGENT DESIGN: William A. Dembski & Michael Ruse in Dialogue by Robert B. Stewart, ed. Minneapolis MN: Fortress Press, 2007....