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            In the previous post, I overviewed the main ideas that have come out of the blog thus far: a broadly deterministic view of the laws of nature as we understand them, an assertion about the nonexistence of a certain class of emergent behavior, and a skepticism with respect to the concept of free will, its logical coherence, and the terms of the traditional debate surrounding it. These views point inquiry in various directions. The discussion of determinism and the laws of nature presupposes a broad worldview often known as naturalism. This post kicks off a deep dive into this worldview and the surrounding ideas.
            As with many philosophical terms, defining naturalism is a messy endeavor. Beginning simply, naturalism claims something like “everything is natural”. This use of the word natural is juxtaposed with supernatural, so naturalism rules out supernatural phenomena (ghosts, spirits, deities) right from the start. In what follows, I’ll also consider naturalism to be coincident with the claims of physicalism and materialism – that everything that exists is physical or material. Going one step further, a central tenant of naturalism is what is known as the “causal closure of the physical” – basically, every physical effect has a physical cause. This is probably the most precise definition we can offer at this point without a significant digression.
            I will, however, insert an aside here. The above definition is very metaphysical in nature. It makes claims about what is, about the intrinsic nature of what exists. My philosophical intuitions tend to point in a more functionalist direction. I like to think that a delineation of everything a physical system does entails a complete description of that system. If you tell me everything a physical system does, every way it interacts with its environment, every way it can manifest to potential observers, then there is nothing left to say about that system. In particular, the question “but what is the system, really?” has no intelligible answer. I’m open to being persuaded on this point, but for now I’ll just note that the explicitly metaphysical aspect of naturalism is not something I’m willing to fully endorse.
            Back to the main thread. Obviously a blog post is not enough room to mount a full-fledged defense of naturalism and everything it entails. I’ll offer justifications for certain naturalistic claims in future posts. For now I’ll just make some general comments on the implications of the philosophy and note areas where the most promising counterarguments might arise. This discussion will suggest further inquiry into the same areas of philosophy that came up in the last post, namely philosophy of mind and moral philosophy, as well as a dangling blog topic – modality (possibility).
            One way to begin to interrogate naturalism is to ask – given naturalism, what is the ontological status of [insert entity that at first doesn’t seem physical or material]? Low hanging fruit first – does God exist? Naturalism says no, notwithstanding certain strands of pantheistic belief that identify the divine with the entire natural world. In my treatment of naturalism, I won’t dwell on the topic of religion, mostly because considering religious objections to naturalism opens up so many additional lines of inquiry – historical, methodological, epistemological, pragmatic. The last post indicated I have enough on the agenda as it is.
            What about the mind? This is where some of the most fundamental objections to naturalism come up. Naturalism claims that everything that exists is made up of the stuff of physics: electrons, quarks, antineutrinos, etc. In particular, my brain is made of this stuff, arranged in a particular way. But what about my mind, the locus of my thoughts and feelings, that strange sensation of constituting a self, my consciousness? What is that made of? Of course, my mind is intimately tied to my brain in some kind of causal way. Damage my brain (in certain ways), damage my mind. Behead me, bye bye mind. But how do we explain the (apparent) existence of the first-person experience of the mind within a naturalistic framework? Is the mind just identical to the brain? It seems to be something else, something extra, something different. A more elegant phrasing of the same conundrum – if I, my brain together with my body, am a (stunningly complex) collection of physical entities, why is it like something to be me? Where does this first-person experience come from? This group of questions is commonly known as the hard problem of consciousness. It is the central issue in the philosophy of mind. Through my whirlwind tour of the free will literature, I’ve come to see it playing important roles in other philosophical debates as well. Later on in this blog, we’ll approach the hard problem through a naturalistic lens.
            The status of moral claims within naturalism is also of interest. If the entire world is composed of physical entities, where do the concepts of moral worth and moral responsibility reside? The point can be sharpened by leaning on the deterministic nature of the laws that govern physical systems. If everything is physical, and physical systems are governed by (largely deterministic) natural laws, I can intelligibly talk about what will happen, but what does it mean to claim what should happen? In other words, naturalism seems to reduce the truths about the world down to descriptive truths (those particles are there, that system behaves in these ways, hey look there’s a supernova, etc.), but morality is expressed in terms of normative claims – one should do x, y is wrong, it’s good to z, etc. Can these ways of speaking about the world be reconciled? We’ll try to address these issues by delving into meta-ethics (the study of the nature of ethics) from a naturalistic perspective.
            Along very similar lines, what happens to the notion of possibility within naturalism? Again, if the universe is physical and governed by natural laws, what does it mean to say something might happen? My “pre-philosophical” view is that there are two senses in which possibility can be discussed within a naturalistic framework. First, there might be genuine (metaphysical) possibility due to inherent randomness in the laws of nature (think quantum mechanics). Second, there will in many situations be some notion of epistemological possibility – saying x might happen is equivalent to saying that whatever will unfold is deterministic, we just don’t know what it is, and x is among the possibilities. We will expand on these ideas when we examine modality within naturalism.
            One important distinction that may come up when considering the intersections between naturalism and the areas mentioned above is that between so-called reductive and non-reductive physicalism. In plain words, reductive physicalism takes the defining credos of naturalism (everything is physical, every physical effect has a physical cause) quite literally. This brand of physicalism can have the effect of reducing or explaining away many of the entities, such as mind or morality, that generated the questions above. Non-reductive physicalism, by contrast, seeks to put such entities on a firmer metaphysical footing by interpreting naturalism’s axioms somewhat differently. Articulating just what this difference in interpretation amounts to strays too far afield for this high-level overview, but it is something that should be contended with in the future. I’ll be advocating for a more or less reductive physicalism.
            So that’s the territory. It’s vast, intricate, and fascinating. Let’s get to it.