In modern philosophy, metaphysics can be categorized into two main types: analytic, often referred to as first philosophy, and naturalized, also known as "scientific" metaphysics. The book "Scientific Metaphysics," edited by Don Ross, James Ladyman, and Harold Kincaid, argues that analytic metaphysics may lack practical value and advocates for a version of naturalized metaphysics. I expressed my general support for this initiative in my previous discussion, though I don't fully align with every contributor.

In this piece, I will focus on the second chapter of the Ross et al. volume, written by Anjan Chakravartty, titled “On the Prospects of Naturalized Metaphysics.” This intricate essay requires familiarity with philosophical and scientific discourse, so instead of a detailed summary, I will highlight key insights from Chakravartty and provide my commentary to clarify the ongoing debate for general readers.

Chakravartty begins by emphasizing that meaningful discussions in science and philosophy necessitate metaphysical considerations:

“Philosophical arguments supporting the validity of belief in scientific entities and processes, such as genes and gene transcription, often rely on concepts traditionally associated with metaphysics, like causation and modality.”

This assertion is both insightful and significant. For instance, the term "gene" is widely used in scientific literature. Historically, the concept of unseen particles that transmit information to create biological molecules was once deemed metaphysical. Greg Mendel introduced the idea of genes in the late 19th century to elucidate observable traits in pea plants.

Despite decades of research following Mendel's discoveries, the existence of genes remained undetectable until advancements in electron microscopy. However, what these microscopes reveal are merely images of DNA strands, which do not equate directly to genes. Some genes consist of RNA, and not all DNA represents genes as carriers of information. Thus, while "gene" is a vital concept for biologists, it encapsulates various physical manifestations.

This complexity extends even further in fundamental physics, where neither electrons nor quarks have been observed directly, yet they are essential components of theoretical frameworks explaining the universe. In contrast to genes, subatomic particles are even more abstract and metaphysical.

This situation does not pose significant issues for scientists or philosophers; however, it leads to what Chakravartty describes as the "realist slippery slope." Many scientists and philosophers maintain a realist stance on entities like genes and particles, believing they genuinely exist beyond mere theoretical constructs.

Consequently, science is not solely based on empirical data. It inherently involves certain pre-empirical commitments, including the assumption of invisible entities and abstract concepts like causation. The slippery slope arises because it's challenging to determine the boundaries of these pre-empirical commitments. If we accept electrons, why not consider philosophical zombies or panpsychism? Chakravartty suggests:

“One might argue that deep metaphysical concepts, such as philosophical zombies, are too distant from scientific inquiry to offer meaningful insights. This implies that pursuing such metaphysics may be an unproductive philosophical endeavor.”

However, the challenge lies in identifying when metaphysical exploration becomes excessive. The goal is not to eliminate metaphysics but to establish criteria for distinguishing valuable metaphysical inquiry from that which lacks epistemic merit. Chakravartty provides guidance on this issue later in the chapter:

“Metaphysics generally relies on a priori theorizing, leading to claims that cannot be empirically tested. It is the absence of substantial empirical grounding that raises concerns about certain metaphysical approaches.”

He further explains:

“Naturalized metaphysics derives its inspiration and limits from the findings of our leading scientific theories, while non-naturalized metaphysics operates without such constraints.”

To illustrate this distinction, consider two contrasting debates in contemporary philosophy of science: one regarding natural selection in biology and the other concerning panpsychism—the idea that consciousness is a fundamental aspect of reality.

Natural Selection: As Chakravartty notes, the central question is whether natural selection acts as a force on biological entities, akin to gravity, or if it merely represents a statistical outcome of interactions at lower levels, like individual organisms.

My colleague Jonathan Kaplan and I have engaged in this debate within philosophy of science journals, where both biologists and philosophers contribute. This discourse remains grounded in empirical biological science, particularly population and quantitative genetics, preventing it from sliding too far down the slippery slope. Consequently, the metaphysical discussions here are closely tied to empirical evidence, even if they stem from a priori theorizing.

Panpsychism: In contrast, theoretical physicist Sabine Hossenfelder's article "Electrons don’t think" critiques panpsychism. She argues that if electrons possess consciousness, this should manifest as observable anomalies in the Standard Model of physics. Hossenfelder concludes that since no such evidence exists, electrons cannot be conscious.

Proponents of panpsychism, like Philip Goff, argue that Hossenfelder misinterprets the concept by seeking empirical evidence, as panpsychism transcends materialism and suggests a dual aspect of reality.

This raises the question of what it means to be a property dualist. Goff, like David Chalmers, posits that while only one type of substance exists, there are two qualitatively distinct property categories: physical and mental. Thus, they contend that Hossenfelder's focus on physical properties neglects the possibility of mental attributes.

This scenario exemplifies the pitfalls of descending into the depths of the slippery slope. Goff and Chalmers' reliance on property dualism serves to shield their theories from critique, but it results in their ideas being disconnected from empirical evidence, rendering them epistemically impotent.

Returning to Chakravartty, he continues to discuss viable scientific metaphysics, noting:

“A core idea of naturalism is the continuity of philosophy, particularly metaphysics, with science. This perspective is crucial to our current discussion.”

This notion aligns with previous discussions regarding the introductory chapter of "Scientific Metaphysics," authored by Harold Kincaid. The interpretation of "continuity" is particularly significant, as some contributors advocate a stronger connection than I find acceptable, suggesting philosophy might be subsumed entirely within science. I hold substantial reasons to contest this view.

Chakravartty makes a critical point, which I fully endorse:

“Metaphysical theorizing is only legitimate when it is grounded in empirical evidence. Nonetheless, the empirical foundation is often misconstrued as science itself, which cannot provide the purely a posteriori content required for legitimacy since scientific knowledge blends a priori and a posteriori elements.”

In essence, scientific metaphysics cannot rely solely on science for validation because science encompasses both empirical and theoretical claims. The grounding that is sensible for both realms—science and metaphysics—must be empirical evidence, whether immediate or indirect. This empirical basis safeguards metaphysics from becoming mired in speculative constructs.

Indeed, science faces similar challenges, as seen in debates surrounding string theory, various interpretations of quantum mechanics, and concepts like parallel universes—all too detached from empirical validation.

[Next time: Scientific vs speculative ontology]