Does accepting methodological naturalism in science necessarily entail accepting metaphysical naturalism as a philosophical consequence, as some philosophers suggest (Maarten Boudry)?

The distinction between methodological naturalism and metaphysical naturalism is among the most important discussions in contemporary philosophy of science. Maarten Boudry and other philosophers argue that accepting the former leads logically to the latter. This claim requires careful analysis, as it has major implications for the relationship between science and religion.

Inadequate Responses to Avoid

From some defenders of separation:

"Methodological naturalism is just a tool, unrelated to metaphysics." This is oversimplification. Methodological naturalism is not completely "neutral"; it contains philosophical assumptions about the nature of scientific explanation. Ignoring these assumptions weakens the position.

"Religious scientists prove the possibility of separation." This is a weak argument. The existence of religious scientists does not settle the philosophical question about the logical relationship between the two positions. The question is not about psychological possibility, but about logical consistency.

"Methodological naturalism is purely pragmatic." This is imprecise. Even a pragmatic position contains philosophical commitments. Claiming that method is "philosophy-free" is itself a philosophical position.

From some defenders of the connection:

"The success of naturalistic science proves metaphysical naturalism." This is a logical leap. The success of a method in a specific domain does not prove it is the only possible method in all domains. This confuses pragmatic success with metaphysical truth.

"Methodological naturalism assumes God's non-existence." This is a conceptual error. Methodological naturalism assumes that scientific explanations must be natural, not that God does not exist. The difference is important.

"The distinction between methodological and metaphysical is contradictory." This claim needs proof. Many contemporary philosophers defend the consistency of the distinction. Asserting contradiction goes beyond the debate.

Why These Responses Are Inadequate

They share a failure to engage with the logical structure of Boudry's and similar arguments. The debate requires careful analysis of the relationship between method and metaphysics.

Precise Definition of Terms

Methodological Naturalism: The position that science, as a practice, should be limited to natural explanations of phenomena. It does not resort to supernatural explanations (miracles, direct divine intervention) in building scientific theories.

Metaphysical/Ontological Naturalism: The position that nature is all that exists. There are no supernatural realities (God, angels, immaterial souls). The universe is causally closed.

The distinction is conceptually clear: the first is a position about scientific method, the second about the nature of existence.

Boudry's Argument and His Supporters

Maarten Boudry in his thesis "Here Be Dragons" (2011) and subsequent papers develops a sophisticated argument:

Stage One: Methodological naturalism is not an innocent "convention."

Boudry argues that methodological naturalism is not merely a "procedural decision," but a position with epistemological justifications. Science adopts natural explanations because they are:
- Testable empirically
- Produce specific predictions
- Falsifiable
- Consistent with the rest of scientific knowledge

Supernatural explanations lack these characteristics, so science excludes them.

Stage Two: Cumulative success justifies generalization.

Naturalistic science has succeeded in explaining phenomena that were historically considered "supernatural" (epilepsy, plagues, meteorological phenomena). This cumulative success justifies expecting that all phenomena will eventually be explainable naturalistically.

Stage Three: Metaphysical naturalism is a reasonable conclusion.

If everything that can be known scientifically has a naturalistic explanation, and if science is our primary way of knowing about the world, the reasonable conclusion is that the world is entirely naturalistic.

Boudry adds: The distinction between methodological and metaphysical is "unstable." Those who accept the former will be gradually pushed to accept the latter.

Critique of Boudry's Argument

First Critique: Confusion between scope and nature.

Methodological naturalism defines the scope of science (it studies nature), not the nature of existence (nature is everything). This is like saying: "Because microscopes only see cells, only cells exist." Science is limited by its method, and this does not mean that what transcends its method does not exist.

Robert Larmer in "Is There Anything Wrong with 'God of the Gaps' Reasoning?" (2002) clarifies: Methodological naturalism is a pragmatic decision about the limits of science, not a metaphysical conclusion about the limits of existence.

Second Critique: Fallacy of generalizing from partial success.

The success of science in explaining certain phenomena does not justify concluding that all phenomena are amenable to scientific explanation. This is inductive generalization that goes beyond the evidence. Especially since there are domains (consciousness, moral values, logical necessity) where naturalistic explanation faces serious challenges.

Alvin Plantinga in "Where the Conflict Really Lies" (2011) argues that this generalization assumes nature is "causally closed," which is a metaphysical assumption that cannot be proven scientifically.

Third Critique: Distinction between evidence and explanation.

Even if we accept that science only gathers naturalistic evidence, this does not mean the ultimate explanation must be naturalistic. For example, archaeology studies material remains but infers the existence of minds that designed them. Similarly, studying the material universe can lead to inferring a non-material designer.

Richard Swinburne in "Is There a God?" (2010) develops this point: Natural evidence can point to supernatural realities, just as material remains point to immaterial minds.

Fourth Critique: Methodological naturalism is not absolutely binding.

Even within science, there is debate about the limits of methodological naturalism. In cosmology, some theories (multiverse, anthropic principle) approach the limits of what can be tested empirically. In cognitive sciences, the hard problem of consciousness pushes some philosophers (David Chalmers) to propose new fundamental properties of existence.

Contemporary Trends in the Debate

"Strict Naturalism" trend (Boudry, Barbara Forrest, Paul Kurtz): They defend the necessary connection between methodological and metaphysical. They see the distinction as an unjustified "concession" to religion.

"Methodological Accommodation" trend (Eugenie Scott, Michael Ruse at one stage): They defend separation for pragmatic and educational reasons. Science must remain religiously neutral to be acceptable in public education.

"Methodological Openness" trend (Stephen Meyer, William Dembski, Michael Behe): They challenge methodological naturalism itself, arguing that science should be open to design explanations when necessary.

"Critical Integration" trend (Alister McGrath, John Polkinghorne, Denis Alexander): They accept methodological naturalism in science but reject metaphysical naturalism. They see science and religion as complementary perspectives.

The Deeper Philosophical Point

The debate reveals a fundamental tension in philosophy of science: What is the relationship between method and truth?

Three possible positions:

1. Strong Scientific Realism: Scientific method reveals complete truth about reality. What science does not grasp does not exist. This supports Boudry's position.

2. Moderate Scientific Realism: Scientific method reveals important truths about reality, but not necessarily all truths. There may be aspects of reality that transcend scientific method.

3. Scientific Pragmatism: Scientific method is a successful tool for prediction and control, but it does not claim to reveal the ultimate nature of reality.

Most contemporary philosophers of science lean toward the second or third position, which weakens Boudry's argument.

Special Case: The Question of Origins

The question of the universe's origin reveals the limits of methodological naturalism. At the point of absolute beginning (t=0), the natural laws themselves need explanation. Here, even strict naturalists resort to concepts that approach metaphysics (multiverse

Where We Stand in This Debate Today

The period 2020-2026 witnessed important developments in this debate. Boudry continued defending his position in joint papers with Jerry Coyne, insisting that the distinction between the two naturalisms is a "diplomatic trick" rather than a coherent philosophical position. In contrast, philosophers like Yujin Nagasawa and Hans Halvorson in his book "The Logic of the Trinity" (2025) developed arguments showing that commitment to methodological naturalism does not entail ontological closure. The debate over the "hard problem of consciousness" also reactivated skepticism about the adequacy of metaphysical naturalism, as prominent naturalist philosophers like Philip Goff acknowledged that consciousness poses a genuine challenge to naturalistic causal closure. In philosophy of cosmology, there has been increased recognition that theories like the multiverse transcend the bounds of empirical testability, weakening the claim that naturalistic science can explain everything "from within." The general trend leans toward recognizing that the jump from methodological to metaphysical is not automatic, though disagreement remains about the extent of method's independence from ontological commitments.

From the Perspective of Rational Preferability (rajḥān ʿaqlī)

The relationship between methodological and metaphysical naturalism presents a paradigmatic case for cumulative assessment:
─ Boudry's argument deserves fair consideration: The cumulative success of naturalistic science is a real datum that should not be minimized, and the distinction between methodological and metaphysical is not as self-evident as some defenders assume.
─ However, the leap from "successful method" to "complete truth about existence" remains an inductive jump that goes beyond the evidence and presupposes what it seeks to prove (causal closure).
─ When we add this datum to others ─ fine-tuning, the problem of consciousness, the ontological foundation of rationality and ethics ─ it becomes clear that metaphysical naturalism pays a steep explanatory price in multiple domains.
─ The rational preference leans toward the view that methodological naturalism is a legitimate scientific practice that does not entail metaphysical naturalism, and that openness to a dimension transcending nature remains a coherent rational position within the cumulative balance.
─ There is no decisive resolution, but the balance of evidence does not support the automatic transition that Boudry proposes.