Atheists don’t believe in god. Atheists do not necessarily reject the supernatural, although most of them do. Atheists do not necessarily believe that the universe is understandable solely in naturalistic terms, although nearly all of them do. Believing there is only the material universe almost certainly makes you an atheist, but being an atheist does not necessarily lead to materialism.
My worldview however, and that of most atheists I know, is metaphysical naturalism. Necessarily, I am also a methodological naturalist, although being a methodological naturalist does not impose metaphysical naturalism.
What’s the difference?
Methodological naturalism is the assumption (most prevalent in science) that the universe and everything in it can be ultimately attributed to natural causes. Science assumes that only by empirical study can we derive understanding of the universe, and we understand the universe with natural explanations. Methodological naturalism does not invoke or reject the supernatural, but assumes it is irrelevant for understanding nature.
This is how science operates. Many theistic philosophers and scientists don’t have a problem with this. Some do. Those that do might say that science should be a search for truth, and we should follow that search wherever it might lead. Why rule out the supernatural a priori? One might reply that supernaturalists unfairly assume that the supernatural exists. The counter reply is that science assumes that the supernatural doesn’t exist, but this is not necessarily the case; science only assumes that the supernatural is irrelevant. Whether either side has a point or not is not the issue here. What I will ask is: how are we to empirically test the supernatural? How are we to derive natural explanations of supernatural phenomenon? A theistic scientist might reply that science is ill-equipped to do so, or that we should not limit science merely to natural explanations or empirical study. But if we did so, would we actually be doing science any longer?
Is not science necessarily as defined, the natural explanation of the world by empirical study? Is this an unfair automatic disqualification of the supernatural? I don’t think so. If it is, all one can fairly say is that science is necessarily limited to naturally explaining only phenomena that can be empirically tested. The supernaturalist would have a good case then for claiming that if there exists something that cannot be explained scientifically, we must appeal to supernatural explanations and some other form of investigation. What such phenomena and other possible methods for investigation might be, I would really like to know.
A Load of Bright has recently made a very good case that even supernatural effects would present themselves naturally and empirically to us, since our sense experience of anything is necessarily empirical and natural. Even someone who has genuinely seen a ghost has had their brain interpret electrical signals from the optic nerve from the eye where light waves have impacted on the retina through the lens, from an external light-emitting/reflecting source. Perhaps then, even if the supernatural exists, we can study its natural effects and explain those naturally. Someone, for example, who tried to explain genuinely seeing a ghost (assuming the viewer wasn’t hallucinating) without mentioning light waves, retinas, optic nerves, eyes, or brains, wouldn’t be doing science, whether the ghost was real or not.
Metaphysical naturalism is the worldview that the natural universe is a closed system, and everything in it can be attributable to natural causes. Strictly speaking, a metaphysical naturalist might not deny the supernatural for the same reason as they wouldn’t deny Easter Bunnies: because it is as big an example of irrelevancy as one can imagine. Metaphysical naturalism would rule out ghosts, spirits, souls, and theistic god(s).
I prefer to refer to myself as a naturalist as oppose to a ‘materialist’ although I know I will raise objections here. I am, of course a metaphysical materialist, but the problem with materialism arises of defining exactly what matter means. Matter and energy are of course interchangeable, but there are forms of “matter” in the universe that are unknown to us. Dark matter and dark energy are the source of great debate and mystery among scientists and may account for over 90% of the composition of the universe. It might be strange to be certain that the entire universe is attributable to matter when we cannot explain the nature of most of it. It is therefore preferable to use the expression ‘physicalist’.
In any event, I do believe that everything in the universe has a natural cause, and everything is ultimately attributable to the workings of natural physical phenomena (as described by physics), as best as we can understand it.
Support for metaphysical naturalism.
What makes metaphysical naturalism so satisfying as a worldview is the fact that it has, as a matter of systematic change (often very quickly, sometimes painfully slowly), replaced supernaturalism so convincingly in explaining the world. Whilst this doesn’t disprove supernaturalism, it does show a definite trend to replace supernatural explanations of the world with natural ones. This trend has continued throughout history through the increase in power of science, and shows no signs of abating.
Science’s incredible success in making sense of the world, explaining phenomena, and predicting with stupefying accuracy the universe around us, without ever needing to resort to a supernatural explanation, lends excellent support to naturalism.
Moreover, we find that supernaturalism tends to exist with increasing ubiquity the further back in the past we go, and to those parts of the world that are deprived of modern scientific understanding. It seems prima facie that supernaturalism was invoked to explain those parts of the world we didn’t understand before science. As science shines a light on a shadow in human understanding, what we find when the dark is removed is not inexplicable supernatural mystery, but a sometimes mundane, sometimes fascinating natural explanation.
Given the phenomenal explanatory power of science, those recesses of mystery of non-understanding that we still don’t understand or science has yet to explain, might require supernatural explanations, but I think we can fairly say this is “god of the gaps” reasoning: find something that is hard to explain or undiscovered yet, and declare that only the supernatural can explain it. Rather, time and time and time again, it has been shown that very often, science does turn out to have the answer after all.
Whilst this does not disprove supernaturalism, it is more and more what we would expect if supernaturalism was false and naturalism was the correct worldview.
Arguments against metaphysical naturalism
Some arguments against naturalism and physicalism are based on the putative (and dubious) consequences of such a worldview, such as nihilism, despair, lack of hope, impossibility of objective morality etc. I don’t believe these charges are true, but they are irrelevant to the truth of naturalism so I won’t consider them here.
One major critique of physicalism is that it cannot account for the human mind. However, proponents of this strategy usually claim that the mind is immaterial and therefore an exclusively material worldview cannot explain consciousness. I believe this begs the question that the human mind is indeed immaterial. It is one thing to propose conundrums and problems for physicalism based on observation and incompatibility between physicalism and consciousness, in favour of another worldview such as supernaturalism and/or theism which explains the human consciousness by dualism. I welcome such philosophical challenges; they are genuine and fascinating, and ultimately need to be resolved one way or the other. It is another situation however to simply assert based on theology that the human mind is immaterial, and that’s that. What is your basis for believing in any immaterial mind? Is it because there are issues of consciousness and conception (such as qualia) that physicalism supposedly cannot explain, or is it because the concept of immaterial minds is what your spiritual beliefs require?
Is physicalism incompatible with consciousness? If not, there would be reason to believe there exists an element of mind that is not attributable to the physical. It is however not fair to say that physicalism is false because there is some element of mind that physicalism (though science) has not yet explained. On the one hand, this is an argumentum ad ignorantiam, and on the other, science has indeed explained many properties of human consciousness in relation to the brain, and neuroscience only looks to get more and more successful in this field. I doubt dualists would seriously nail their colours to this mast, as it is always possible the dualistic ship might sink one day when science does fully explain human consciousness in purely physical terms. At the moment, whilst we understand the brain very well, consciousness is still not something that we fully understand, and no physicalist would deny this. A far more potent case can be made against physicalism if facts are presented that it is impossible for physicalism (and indeed science) to explain even in principle without resorting to a dualistic explanation.
I’ll briefly consider two such propositions.
The first is qualia. Wikipedia says “They can be defined as qualities or feelings, like redness or pain, as considered independently of their effects on behavior and from whatever physical circumstances give rise to them. In more philosophical terms, qualia are properties of sensory experiences.”
Frank Jackson’s thought experiment called the Knowledge Argument is:
“Mary the colour scientist knows all the physical facts about colour, including every physical fact about the experience of colour in other people, from the behavior a particular colour is likely to elicit to the specific sequence of neurological firings that register that a colour has been seen. However, she has been confined from birth to a room that is black and white, and is only allowed to observe the outside world through a black and white monitor. When she is allowed to leave the room, it must be admitted that she learns something about the colour red the first time she sees it — specifically, she learns what it is like to see that colour.”
Therefore the Knowledge Argument claims:
1. Before her release, Mary was in possession of all the physical information about colour experiences of other people.
2. After her release, Mary learns something about the colour experiences of other people.
3. Before her release, Mary was not in possession of all the information about other people’s colour experiences, even though she was in possession of all the physical information.
4. There are truths about other people’s colour experience that are not physical.
5. Physicalism is false.
The philosopher Daniel Dennett however “argues that Mary would not, in fact, learn something new if she stepped out of her black and white room to see the color red. Dennett asserts that if she already truly knew “everything about color”, that knowledge would include a deep understanding of why and how human neurology causes us to sense the “quale” of color. Mary would therefore already know exactly what to expect of seeing red, before ever leaving the room. Dennett argues that the misleading aspect of the story is that Mary is supposed to not merely be knowledgeable about color but to actually know all the physical facts about it, which would be a knowledge so deep that it exceeds what can be imagined, and twists our intuitions.”
Dennett also proposes that there is a problem of our language to communicate. Had Mary never seen a triangle it wouldn’t be too hard to describe the physical aspects of a triangle to her, allowing her to imagine what one looks like. That it is harder to do so for colour doesn’t make it impossible, nor does it prove the existence of qualia.
David Lewis also rejects the qualia thought experiment by denying that Mary gains knowledge in that sense implied, because qualia communicate abilities, such as how to experience red. He draws a distinction between informative knowledge and the knowledge of ability. Mary cannot use her experience to gain experiential knowledge of the colour red because the thought experiment limits her to informative knowledge. Just as Mary cannot know what is it like to swim or fly from inside the room; Lewis argues that physicalism is not threatened by supposed qualia because there are different forms of knowledge. In other words, the thought experiment is fallacious.
A necessary but not sufficient criterion of a successful worldview is that it is internally consistent. Any metaphysical position that is internally consistent is unassailable, but this doesn’t make it correct.
Are metaphysical naturalism and physicalism internally consistent?
The very intelligent and sophisticated theologian Alvin Plantinga thinks not. He proposed the Evolutionary Argument against Naturalism and asks:
“But isn’t there a problem, here, for the naturalist? At any rate for the naturalist who thinks that we and our cognitive capacities have arrived upon the scene after some billions of years of evolution (by way of natural selection and other blind processes working on some such source of genetic variation as random genetic mutation)? The problem begins in the recognition, from this point of view, that the ultimate purpose or function of our cognitive faculties, if they have one, is not to produce true beliefs, but to promote reproductive fitness. What our minds are for (if anything) is not the production of true beliefs, but the production of adaptive behavior. That our species has survived and evolved at most guarantees that our behavior is adaptive; it does not guarantee or even suggest that our belief-producing processes are reliable, or that our beliefs are for the most part true. That is because our behavior could be adaptive, but our beliefs mainly false.”
What Plantinga attempts to show is that if our senses are fairly reliable, an assumption almost all us who aren’t epistemologically-nihilistic dire sceptics make, there is a conflict between naturalism as a knowledge-enabling worldview and evolution which, he argues, would not select for truth content of our cognitive abilities, but only for adaptive success. In other words, you might see a tiger running towards you but your senses might tell you that there is a rather rancid-looking bird coming towards you; either way you flee and your cognitive senses have ‘succeeded’; they do not necessarily select for truth.
There are not many arguments against naturalism or physicalism worthy of consideration, but this is a very important one. If Plantinga is correct, naturalism and/or evolution suffers a severe blow. If Plantinga is wrong, one of the strongest possible cases to be made against the self-consistent constitution of metaphysical naturalism is dispelled. Remember that self-consistent stable worldviews are unfalsifiable either way. One can refute a worldview by showing it to be internally inconsistent.
Unfortunately for Plantinga and presuppositional theists who assert that theism is the only stable worldview, Plantinga fails. (Probably because, in my opinion, he has missed important facts about how evolution works.)
Our brains employ a virtual simulation software that builds an internal representation of the external world through our cognitive apparatus. It is not perfect, and the truth is we do not, nor does any lifeform in existence, ever see the “real” world. We see a miniscule portion of the electromagnetic spectrum that reflects off objects and into our eyes. Our visual balance is such that red is at one end of our optical perception and violet at the other. Insects also have a window to the outside world similar in length to ours, except they are blind to red and see further into the ultra-violet than we can. Bats do not see with their eyes at all (a rather fundamental design flaw one might think), but instead build a structure of the world in their minds using echo-location. Our brain attributes labels to varying perceptions of external stimuli. Light of a certain wavelength is coded as “red” in our brains; “blue” to refer to another wavelength of light. Richard Dawkins has suggested, very tantalisingly and very convincingly, that bats’ brains might attribute colours to different textures that their sound waves reflect back off. Colour is a label that a brain attributes to certain stimuli. There is nothing impossible about another form of life smelling colours! Remember, the brain is simply building a simulation in our heads of what is outside. For evolution to allow naturalism to give a worldview for reliable knowledge, this simulation software must not be capricious or lucky enough to allow us to survive. It must give us reason to believe and expect that our senses report “truth”.
Fortunately, for metaphysical naturalists, that is exactly what evolution has produced. Ebonmuse says of Plantinga: “this argument is not just wrong, it is obviously wrong. An atheist has more than sufficient grounds to believe that their sensory and cognitive faculties are reliable, and it is not just probable but inevitable that a process of naturalistic evolution would result in this.”
“Our minds and senses, like all other adaptations of living species, were designed by evolution. And like all other adaptations, they could only have persisted to the degree that they aided our survival. If they did nothing but generate false beliefs, then at best, they would not harm our chances of survival, and far more likely would substantially decrease them. In either case, they would soon be eliminated by natural selection – in the latter case because they were an impediment to survival, in the former case because they were simply a waste of energy that could more usefully be spent elsewhere (like the eyes of blind cave fish). (The human brain consumes a substantial fraction of the body’s total oxygen and energy consumption. Natural selection could never maintain such a costly adaptation unless it conferred substantial survival benefits.)”
“What Christian apologists have ignored is that the ability to accurately perceive one’s environment and respond appropriately is essential to survival.”
Ebonmuse continues: “A bacterium has none of a human being’s rich mental life, of course, and apologists such as Plantinga argue that while evolution would select for correct actions, it would not necessarily select for correct beliefs. But though this could be true for creatures whose actions are decoupled from their beliefs, human beings are not like this. If a creature will face more situations in its lifetime than its genes can explicitly program it for – if it cannot live solely by the autopilot of instinct, as human beings cannot and do not – then that creature must perceive its environment correctly in order to respond correctly. Accurate belief is the only sure way to produce correct action.”
bd-from-kg over at the Internet Infidels discussion forum discussing the Plantinga EAAN says:
“Now Plantinga seems to think that, in order for the contents of beliefs to be subject to natural selection (so that beliefs with true contents are more likely to be selected) those contents would have to have a causal influence on our actions. But that’s not true.”
“Take [a] dangerous bridge for example. (We’ll assume here that it really is dangerous.) Natural selection clearly could select for cognitive processes that tend to produce (under the conditions that actually obtain) beliefs whose content is that the bridge is dangerous. For example, those whose [cognitive processes] tend to yield beliefs with the content that the bridge is safe might tend to be at a severe reproductive disadvantage as a result of dying at an early age. So while natural selection cannot select directly on the basis of the contents of beliefs, it could certainly select for cognitive processes that tend to produce beliefs whose contents are true.”
“With this understanding, it’s clear that the question of whether the content of a belief “enters the causal chain leading to behavior” is a red herring. Of course it doesn’t – not strictly speaking anyway. The content of a belief is a proposition, and propositions do not enter into causal chains. But it doesn’t matter. Natural selection can select for cognitive processes that produce beliefs with true contents, and this is what matters.” (Emphasis mine).
What this proves is that natural selection can most certainly work on cognitive faculties, and these faculties report information to the brain. Whether a belief is part of the causal chain or not is irrelevant; our sense organs are, and as much as evolution can select for improving sense organs (which it necessarily can and does) it would also select for beliefs based on those senses.
So, we know that evolution can select for belief-content indirectly. Plantinga however says:
“For every true adaptive belief it seems we can easily think of a false belief that leads to the same adaptive behavior” and concludes that “The fact that my behavior (or that of my ancestors) has been adaptive, therefore, is at best a third-rate reason for thinking my beliefs mostly true and my cognitive faculties reliable–and that is true even given the commonsense view of the relation of belief to behavior. So we can’t sensibly argue from the fact that our behavior (or that of our ancestors) has been adaptive, to the conclusion that our beliefs are mostly true.”
But there is no reason at all to believe that for every adaptive belief there is a false belief that leads to the same behaviour! That is an enormous and absurd assertion.
It might be possible that for a single specific limited event, say, running away from a tiger, there might be a corresponding false belief that happens to correspond with the true state of affairs. But what possible reason is there to think that our brains would construct, or that the real world would conspire to confect, false beliefs for every possible (or even the majority of) scenario(s) that we might encounter?
Bd continues: “most of our behavior is not of the simple “reactive” kind (like running away from a tiger) that Plantinga likes to talk about, but is “goal-oriented”. In order to achieve even a simple goal it is generally necessary to act on the basis of a great number of beliefs, all of which contribute in an essential way to the achievement of the goal. It’s just ludicrously implausible that a set of false beliefs might “just happen” to contribute in an analogous way to the achievement of the goal.”
Most of our everyday actions, and most importantly, the ones that evolution would select for, are based on such a complex interweaving of self-confirming beliefs that the falsity of even a few of them would result in terminal errors. Evolution by natural selection would most definitely indirectly select for generally true beliefs by selecting generally reliable sense organs.
It remains for theistic philosophers to raise further objections to metaphysical naturalism and philosophers better learned than myself to defend it further.
I will not suggest so ambitious a proposal that metaphysical naturalism or physicalism is the only successful worldview at making knowledge possible (as theistic presuppositionalists do in reverse). A case has been made that a natural closed system purely understandable as such allows science to function and induction to work. If supernatural entities could impinge on the natural world and alter laws and substance, induction would not be as reliable as it is. In fact, a world where “miracles” are possible would obviate scientific research as we know it, if not render our senses useless to understanding some facet of reality. I will not make that case here, but it is an interesting counter-proposal to theists. I feel grateful in the reasonable certainty that we do live in a purely naturalistic universe where no contrivance of the imagination of man can reign with impunity over the observed laws of cause and effect , or interfere with our world and ability to understand it based on fiat.
The primary alternative to naturalism, physicalism, and in effect monism, is dualism. Dualism and theism might very well be consistent with any conceivable state of affairs. In this respect they are consistent metaphysical theories so this is to be expected. At this point I prefer to invoke the ontological hedge trimmer known as Occam’s Razor and remove the superfluous entity. Dualism might account for a theory of mind, but monism and physicalism can do so as well. A creator-being could have created the universe and everything in it, including man, but we do not need to postulate such an entity to understand anything. The world makes just as much sense, in fact even more sense, without referring to anything beyond the natural. Supernaturalists will counter with the standard arguments from Teleology and Kalam; atheists will reply that the Argument from Design begs the question and is insufficient, and point out the natural explanation of evolution is not only explanatorily superior, it posits fewer extraneous entities; atheists will apply an infinite regress and charge of special pleading to an impossibly-complicated being that never had a cause yet created a complicated universe that demands one.
As Laplace said to the Emperor of France (Napoleon Bonaparte) after describing the workings of the planets in the solar system, in response to the question of why the figure of god did not appear in the calculations: “Je n’ai pas besoin de cette hypothése”; that is: ‘I did not need to make such an assumption.’
What metaphysical naturalism and physicalism do is reduce the ontological count in the universe. What could be explained with 50 supernatural entities could be explained with 25. What could be explained with 25 supernatural entities, djinns, ghosts, or gods could be explained with 12. What could be explained with 12 gods might be explained just as well and less wastefully with 6. But why 6 when 3, or (three gods in) one if that is your preference? To quote Christopher Hitchens: “Surely even a monotheist would be grateful for Ockham’s razor at this point? From a plurality of prime movers, the monotheists have bargained it down to a single one. They are getting ever nearer to the true, round figure.”
A Defence of Naturalism: http://www.infidels.org/library/modern/keith_augustine/thesis.html
Rationalism vs Empiricism: http://plato.stanford.edu/entries/rationalism-empiricism/