A Theory of Reductive Naturalism: The Metaphysical Foundations of Non-belief

Introduction

What do you believe about God? What about global warming? Do you think euthanasia should be legalised? What about bible study in schools? Whatever your answer to these questions, it is very unlikely that you hold your views in isolation, independently of all your other opinions and perspectives. That’s not how human minds work. Instead, we hold our views in the context of a large set of overlapping and interconnected beliefs about what the world is, how it works, and why things are the way they are. This very large, overarching set of beliefs and conceptions about the world is what I call a ‘worldview’. When ideas become successful or popular, it is very rarely because of the specific merits of one idea considered in isolation. Rather, ideas are usually ‘sold’ as part of a ‘package deal’ – a set of interconnected, internally coherent beliefs about the world which people find attractive. Socialism, Fascism, Christianity, Humanism, and Environmentalism are all examples of such worldviews. As my choice of examples shows, the effect that such worldviews has on the world varies dramatically – ideas can shape the world for better or for worse. If, therefore, we want to shape the world for the better, we need to spread good ideas, and to do that we need to package these ideas in a way that people find attractive. To put it another way, it is not enough to just be right about a whole bunch of unrelated issues. Rather, one needs to incorporate these positions into a unified conceptual whole, to provide a worldview that people find intellectually and emotionally attractive. My aim in this short article is to present an outline of the key points concerning what such a worldview might look like from a Rationalist/Humanist/Atheist perspective. Specifically, the view that I am outlining is a form of reductive naturalism, the meaning of which I will explain shortly. It is a metaphysical theory, meaning that it makes claims about what exists in the world. I do not claim that this is the only possible naturalistic worldview that one can develop, but I do think it is a particularly compelling one which is worthy of serious consideration.

Reductive Naturalism

To begin, I must first explain what I mean by the term ‘naturalism’. This word is used in a variety of ways in everyday language, but in this context I am using it with reference to a particular set of philosophical positions concerning what sorts of things exist in the world. Put most simply, naturalism holds that only the natural world exists. While there is no generally accepted definition of ‘natural’ in this context, the usual conception is that the natural world includes all things that are not supernatural. Supernatural entities are such things as ghosts, spirits, magical forces, immaterial souls, gods, and immaterial forces like yin-yang from Chinese philosophy. Such supernatural entities are typically thought to be highly distinctive from anything that exists in nature in that they are not made up of matter, and do not follow determinate causal laws in the way the natural world does. I should emphasise that natural entities include not only things like particles, organisms, and planetary bodies, but also man-made artifacts like computers and political institutions. The relevant distinction is thus not between natural and artificial, but rather between natural and non-natural or supernatural. Thus understood, naturalism is simply the position that there are no non-natural or supernatural entities.

The version of naturalism that I am here defending is reductionist, meaning that according to this view, everything that exists is either a fundamental particle, or is something that exists and holds all the properties that it does solely in virtue of the arrangements and interactions of such fundamental particles. Another way of putting this is that according to reductive naturalism, if one specified the exact configuration of all the fundamental particles in the entire universe, then this would also be sufficient to determine all the properties of everything that exists within the universe. There is nothing ‘left out’ of reality beyond the arrangements of fundamental particles. A few points of clarification are necessary here. First, when I speak about ‘fundamental particles’ I do not necessarily assume that these are the same as what physics currently regards to be the fundamental particles of nature (quarks, electrons, photons, etc). Perhaps they are, or perhaps they are something yet more fundamental that we have yet to discover. All that is important to my case is that there are a determinate, relatively small number of such things, and that they follow causal laws in principle describable by a ‘completed physics’. Second, when I say that the arrangement of fundamental particles is sufficient to determine all properties about everything that exists, I am advocating a theory of ontology (what exists), not a theory of epistemology (how we know) or semantics (what words mean). To consider a particularly tricky example, according to reductive naturalism, the statement ‘Bob loves his wide’ must ultimately be either true or false in virtue of some state of affairs concerning particular arrangements of fundamental particles. This is not to say, however, that we come to know whether Bob loves his wife by examining states of fundamental particles. Nor is it to say that when we say ‘Bob loves his wife’ we are in any way actually thinking about fundamental particles. Rather, my claim is about what exists in the world that makes this claim true – the so-called ontological basis of the fact that ‘Bob loves his wife’. The claim of reductive naturalism is that even highly abstract and complex states as this ultimately pertain in virtue of the arrangement of fundamental particles. Thus, there is nothing outside of or beyond such particles and their interactions that is needed in order to bring about the state of Bob loving his wife. I am thus explicitly disputing the claim made by some philosophers that immaterial minds or Platonic forms or other non-natural entities are necessary in order to account for all the various phenomena that we know about in the world.

Even given these clarifications, many people typically find this reductive naturalism intuitively implausible. How, they say, can you claim that the interactions of protons and electrons are all that there is to such complex, indescribably rich phenomena as human emotions? A large part of the implausibility of my position, however, is removed once we consider the reduction hierarchically. That is, rather than trying to imagine jumping directly from subatomic physics to human emotions, we should instead think about the stages in which this reduction occurs. Subatomic physics underpins the structure and properties of atoms, which in turn bind together to form molecules. Molecules join together through various types of chemical bonds to form macromolecules like proteins and DNA which make up the cells of the human body. Different types of cells with different functions combine together to form tissues and organs, each with their own role in supporting the life of the organism. In the case of the human mind, neurons connect together in complex networks to form mental representations of various concepts, including ultimately those of loving another person. Considered in this incremental manner, I think the notion that facts about human thoughts and emotions are ultimately reducible to facts about brain states, which in turn reduce to facts about neuronal firing patterns, then down to proteins, molecules, and atoms, is far more plausible than it is if we think simply of jumping from atoms straight to the mind in a single leap.

The utility of a philosophical theory ultimately is determined by how useful it is in accounting for various phenomena that we wish to explain in the world. In the case in question, two of the most difficult phenomena that have led many people to posit entities beyond those of the natural world are the human mind and moral values. In this short article I have space only to very briefly consider these complex subjects, and I certainly do not claim to have a complete philosophical account of either. Nevertheless, I do wish to at the very least sketch the outlines of how a reductionist naturalistic worldview can account for the existence of both mind and morality in a way that provides a space for such phenomena without needing to posit the existence of any additional, non-natural entities.

Before doing so, however, there is one final concept (borrowed from physics) that I must introduce, namely the distinction between a microstate and a macrostate. A microstate is a single complete configuration of all the fundamental particles in a system. A macrostate, by contrast, is a set of microstates that share some property of interest. Macrostates thus refer to ‘higher level’ phenomena, whose existence is nevertheless wholly dependent upon the particular microstate the system is in. For instance, one example of a microstate is the exact description of all the positions and velocities of the air molecules in a room. We can then consider various macrostates which are higher-level properties that nevertheless are entirely determined by the microstate that the particles in the room reside in. refers to the set of all such microstates in which the room has a particular temperature. One example of a macrostate would be ‘the air temperature in this room is 30 degrees Celsius’. This macrostate refers to the set of all possible microstates that give rise to this temperature. Even though there are many possible microstates that can instantiate a single macrostate, the temperature of the room is still determined completely by the microstate. The macrostate is thus just a useful ‘higher order’ concept we use to refer to sets of microstates that are similar in some relevant way.

Applications: Mind and Morality

Applying this distinction between microstates and macrostates to the cases of the mind and morality, we see that under the reductive naturalistic worldview, mental and moral states of affairs can both understood to be a kind of macrostate. In the case of the mind, examples of macrostates could be ‘he perceives the colour red’, ‘she remembers her grandmother’s face’, or ‘I believe that it will rain tomorrow’. These are all mental states of affairs which are expressed in a psychological language involving appeal to believes, perceptions, desires, etc. According to the theory of reductive naturalism I am advocating, all such mental macrostates ultimately exist in virtue of the (exceedingly large) number of microstates that are capable of instantiating them. There is, for example, a very large number of possible ways the atoms in my brain could be arranged such that they correspond to being in a state of ‘deciding’. Indeed, it is possible that microstates quite different to those which exist in my brain are also capable of instantiating mental macrostates, such as the arrangements of atoms making up the circuitry of an artificial intelligence. This position in the philosophy of mind is known is functionalism, and holds that mental states are constituted by the functional workings of a given system, and that different physical systems may be capable of producing the same functions and therefore of yielding the same mental phenomena. The exact details of functionalism are not important here, the point is simply that such a view fits very readily within the reductive naturalist paradigm that I have been developing, and is capable in broad terms of making sense of how mental states can exist in a purely material world. The key idea, then, is that mental states are not some mysterious things that cannot be accounted for in the natural world. Rather, appeals to mental states such as beliefs, desires, perceptions, and, even acts of free will, ultimately refer to very complex bundles of possible arrangements of fundamental particles. We cannot possibly specify in detail exactly what all these arrangements of particles look like, but nor do we need to, as the arrangements are defined functionally by the higher-level properties they instantiate. There is of course no need to replace such psychological terms with talk of fundamental particles, because that would distract from our purpose and lead us to getting bogged down in irrelevant details. The point of this analysis, rather, is that such psychological language and the mental states they refer to can fit quite comfortably within a naturalistic worldview, without needing to appeal to the existence of any additional non-natural entities.

We can apply much the same analysis to the case of morality. Morally good macrostates can be understood as states of affairs conducive to the flourishing or wellbeing of sentient creatures. Morally bad macrostates, by contrast, would be states of affairs that bring about the suffering and misery of sentient creatures. Obviously we would need to articulate in more detail what we mean by terms like ‘wellbeing’ and ‘misery’, however since we can readily identify examples of each I take it that these terms, while fuzzy, have a robust meaning that is sufficient for our purposes here. This position corresponds to the metaethical theory of reductive moral naturalism, though once again, the details of this theory are not of prime importance here. What I want to emphasise is simply the fact that moral states of affairs can be readily accorded a place in this naturalistic worldview in accordance with whether or not a particular microstate instantiates a macrostate that is conducive to wellbeing or misery. Thus, when we say something like ‘killing for fun is morally wrong’, this statement is true in virtue of the fact that the various microstates which instantiate the act of killing (obviously there are many ways to kill someone) also instantiate a macrostate in which the wellbeing of sentient creatures is diminished relative to a comparable macrostate in which this act of killing did not occur. There is no need to appeal to the existence of God or any other transcendent source of morality for such moral macrostates to pertain, as they exist purely in virtue of the fact that certain arrangements of fundamental particles instantiate the wellbeing of sentient creatures to a greater extent than other arrangements. Of course, whether one is motivated to act so as to bring about morally good states of affairs is another question entirely. My point here is simply to argue that the existence of morally good states of affairs is readily explicable under a reductive naturalistic worldview.

One possible line of objection to my arguments is that we still do not have a very good understanding of precisely how mental or moral states of affairs arise from (or ‘supervene on’) the interactions of fundamental particles. In particular, there is a sizeable gap in our knowledge between the level of the functioning of single neurons and the emergence of complex mental behaviours and sensations in large networks of neurons. As such, it might be argued that to claim that we can say the latter arise solely from the interactions of the former is premature. In response, I would argue that it is in fact not at all premature to make such an inference. Recall that I am not claiming we have a complete theory of how all of nature works – science is an ongoing endeavour. All I am asserting is that we can account for the core phenomena that we need to, including the mind and moral value, without needing to appeal to any entities outside of the natural world. In doing so, I have given an account as to how the mind and morality can be conceptualised in a reductive naturalistic worldview – I have given ‘a place where they can fit’ in a naturalistic ontology. For this to be plausible, all that is needed is sufficient reason to think it plausible that higher order phenomena such as the mind can potentially arise solely as a result of the interaction of fundamental particles. And I think that the current state of knowledge in physics, chemistry, biology, neuroscience, and psychology is more than sufficient to affirm that such a belief is plausible. Certainly we don’t have the full explanation as to how this occurs, but I think we have ample evidence to infer that it is plausible that it does. Most everyone is willing to believe that the immensely complex behaviour of financial markets arises purely as the result of the financial activities of individual traders and corporations, despite the lack of a detailed theory as to how exactly this occurs. Likewise, no one would seriously argue that fluid turbulence is the result of anything other than the interaction of molecules in the fluid, even though our understanding of the physics of fluid dynamics is still relatively poor. I thus content that we are similarly in a position to affirm the plausibility of mind and morality arising purely from the result of neural activity in the brain (and hence ultimately the interactions of fundamental particles), even though we lack a complete theory as to how this occurs.

Conclusion

While I have argued that we can plausibly consider complex mental and moral macrostates as existing solely in virtue of the interactions of fundamental particles, I have not provided any arguments to prove that this must be the case. There may well be entities that exist outside of the natural world, and therefore the theory I have sketched here may constitute a drastically incomplete worldview. My argument, however, is that a reductive naturalistic worldview has sufficient explanatory power to account for the existence of all the phenomena we would wish it to. Furthermore, reductive naturalism is a highly parsimonious worldview, meaning that it posits only the existence of the natural world (whose existence almost all worldviews accept), and nothing else besides. My argument, therefore, is that if we can account for all that we need to from the natural world alone, then we have no reason to posit the existence of anything beyond the natural world. As to the existence of entities outside of nature we, like Laplace, therefore have ‘no need for that hypothesis’.

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One thought on “A Theory of Reductive Naturalism: The Metaphysical Foundations of Non-belief

  1. What would make something ‘supernatural’? An invulnerability to reductive explanation? How would we propose to know something which does not participate in any sort of explanatory reduction?
    These are the questions which sank substance dualism, and eventually, ‘theories of truth’.

    Like

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