EXPLANATORY ARGUMENTS

A brief explanation of explanatory arguments

Introduction

Philosophers are not only in the business of deducing conclusions from axioms, nor merely describing the world as it seems to them; rather, they are deeply concerned with explaining why things are the way they are. Explanation is central to philosophical practice. Whether the topic is consciousness, morality, laws of nature, modality, or the nature of mathematical entities, philosophical arguments often aim not just to tell us what is the case, but to tell us why it is the case. This makes explanatory arguments — arguments that hinge on considerations of explanatory power — central to philosophical methodology.

This article aims to provide a detailed analysis of explanatory arguments, their structure, their applications, and the ways in which they might be resisted. While the core notion underlying explanatory arguments — inference to the best explanation (IBE) — is familiar from both philosophy and science, the application of explanatory arguments in philosophy presents unique challenges. Unlike scientific contexts, where explanatory hypotheses are often evaluated by empirical predictions, philosophical explanatory arguments frequently operate in domains where empirical access is limited or entirely absent. Thus, evaluating explanatory arguments in philosophy requires not only clarity about the structure of the arguments themselves but also a robust framework for assessing explanatory virtues and identifying potential weaknesses.

Explanatory arguments can be found across nearly every major subdiscipline in philosophy. In the philosophy of religion, the fine-tuning argument appeals to explanatory considerations to support theism over naturalism. In epistemology, explanatory arguments are used to assess the reliability of our beliefs in light of evolutionary or sociological accounts of belief formation. In metaphysics, philosophers argue over which theory of laws of nature best explains the regularities we observe. In ethics, moral realists and anti-realists dispute whether moral truths best explain our moral intuitions. In the philosophy of mind, questions about the explanatory adequacy of physicalist theories loom large.

Despite this broad applicability, explanatory arguments in philosophy remain controversial. Some philosophers are deeply skeptical about the epistemic significance of explanatory considerations, especially in cases where no empirical adjudication is available. Others view explanatory arguments as indispensable tools for navigating between competing theories, especially in metaphysical or conceptual domains.

In what follows, I will lay out a comprehensive framework for understanding and evaluating explanatory arguments. I begin with a detailed motivating example — the fine-tuning argument for the existence of God — which will serve as a recurring reference point throughout the paper. I then present the general structure of explanatory arguments, discuss the key explanatory virtues that such arguments typically invoke, and analyze how explanatory arguments operate across different philosophical domains. I then turn to a range of strategies for resisting explanatory arguments, including both direct attacks on their premises and more global challenges to their epistemic force. Finally, I explore broader meta-philosophical questions about the role of explanation in philosophical reasoning.

My hope is that this detailed treatment will help bring clarity to an important but sometimes poorly understood style of reasoning, and that it will facilitate a more precise understanding of when and how explanatory arguments succeed — and when and how they fail.

A Motivating Example: The Fine-Tuning Argument

To understand how explanatory arguments function in philosophical practice, it is helpful to begin with a concrete example. Among the most frequently discussed explanatory arguments in contemporary philosophy is the so-called fine-tuning argument for the existence of God. The fine-tuning argument is not only prominent in debates in the philosophy of religion but also serves as an instructive illustration of the structure and rhetorical force of explanatory reasoning more generally.

The Fine-Tuning Datum

Modern physics tells us that the universe is governed by a set of fundamental physical constants — such as the gravitational constant, the fine-structure constant, the strength of the strong and weak nuclear forces, and the mass ratios of fundamental particles. What is striking about these constants is that they appear to be “fine-tuned” for the existence of life. That is, had these constants been even slightly different from their actual values, the universe would not have permitted the existence of complex, conscious life. Galaxies would not have formed, stars would have burned out too quickly, atoms would not have bonded in stable ways, or the universe would have collapsed on itself shortly after the Big Bang.

This observation constitutes what we might call the fine-tuning datum — the empirical fact that the values of the physical constants lie within an extraordinarily narrow range that permits the existence of life. Crucially, this datum is not in dispute. Both theists and atheists acknowledge that the constants are fine-tuned in this sense. The disagreement concerns how best to explain this fine-tuning.

The Competing Hypotheses: Theism and Naturalism

The fine-tuning datum invites explanation. Why do the constants have life-permitting values rather than life-prohibiting ones? Philosophers and physicists have proposed a range of possible explanations, but for simplicity, let us consider just two broad hypotheses:

• T1: Theism. There exists a divine being — an all-powerful, all-knowing, and perfectly good God — who created the universe with the intention of producing conscious, morally significant life.

• T2: Naturalism. The universe is the result of non-teleological natural processes. There is no divine agency or intentional explanation for why the constants have the values they do.

The fine-tuning argument is then framed as an explanatory argument for preferring theism over naturalism. It does not purport to prove theism; rather, it claims that theism provides a better explanation of the fine-tuning datum than naturalism does.

The Structure of the Fine-Tuning Argument

The structure of the fine-tuning argument exemplifies a general explanatory schema that can be summarized as follows:

1. There exists a datum D.
   (D: The physical constants of the universe are fine-tuned for life.)

2. There are two competing hypotheses, T1 and T2.
   (T1: Theism; T2: Naturalism.)

3. D is surprising under T2.
   (Under naturalism, it is highly improbable that the constants would be life-permitting.)

4. D is not surprising — and indeed expected — under T1.
   (Under theism, it is likely that the constants would be life-permitting, given God’s intention to create life.)

5. Therefore, T1 better explains D than T2.

6. Therefore, all else being equal, T1 is to be preferred over T2.

This pattern of reasoning is common across philosophical discourse. A datum is identified; two or more theories are evaluated in terms of how well they explain that datum; and the theory that provides the better explanation is provisionally endorsed.

Strengths and Weaknesses of the Argument

The power of the fine-tuning arguments lie in their appeal to explanatory considerations. Faced with the remarkable precision of the physical constants, theists argue that this precision cries out for an explanation — and if so, what kind of explanation it demands.

Yet critics of the fine-tuning argument have raised a number of challenges. Some deny that the fine-tuning datum is as remarkable as it is sometimes portrayed (perhaps because life could have arisen under different conditions). Others argue that naturalism can explain the fine-tuning.

Still others challenge the explanatory virtues of theism. Is the existence of a divine being really a better explanation, or does it raise further questions? Is it legitimate to appeal to intention-based explanations in the context of fundamental physics? How do we assess the prior probability of theism?

These questions illustrate the complexities involved in evaluating explanatory arguments, and they will be taken up in later sections. For now, the fine-tuning argument serves as a useful illustration of how explanatory arguments work in general — and of how they can be both powerful and contentious.

The General Structure of Explanatory Arguments

Having examined a motivating example in detail, we are now in a position to generalize. What makes the fine-tuning argument an explanatory argument is not its subject matter, but its form. Explanatory arguments are governed by a recognizable logical and epistemic structure. They are not deductive arguments in which the truth of the premises guarantees the truth of the conclusion, nor are they inductive generalizations. Rather, they belong to a family of arguments known as inference to the best explanation (IBE), a form of reasoning in which we infer that a certain hypothesis is true — or at least epistemically preferable — because it explains a given phenomenon better than competing hypotheses.

In this section, I will develop a general framework for understanding explanatory arguments. I begin with the basic schema, and then move on to discuss the explanatory virtues that typically guide such inferences. I also consider the epistemic status of explanatory inferences and their place within the broader landscape of philosophical methodology.

A Basic Schema

The structure of a typical explanatory argument can be captured by the following six-step schema:

1. Data (D): There exists some datum D that requires explanation.

2. Competing Theories (T1, T2): There are two or more competing hypotheses or theories — T1, T2, etc. — which purport to explain D.

3. Surprise Under T2: The datum D is surprising, improbable, or otherwise unexpected under theory T2.

4. Expectation Under T1: The datum D is not surprising — or is positively expected — under theory T1.

5. Explanatory Superiority: T1 explains D better than T2.

6. Epistemic Preference: Therefore, all else being equal, we should prefer T1 over T2.

This schema is deliberately abstract. It is intended to apply across a wide range of contexts: metaphysical, ethical, epistemological, and empirical. Its force depends heavily on what we mean by “surprising,” “expected,” and “better explains.” These notions are tied to explanatory virtues, which are evaluative dimensions along which theories can be compared.

Before elaborating on these virtues, it is important to note that this form of argumentation is fundamentally contrastive. The strength of an explanatory argument does not depend solely on how well T1 explains D in isolation, but on how well T1 explains D relative to its competitors. Thus, even if T1’s explanation is not perfect, it may still be epistemically preferable if T2 fares worse.

Probabilistic Interpretation

Many explanatory arguments implicitly rely on probabilistic reasoning. The language of “surprising” and “expected” can be formally interpreted in terms of conditional probabilities:

• Pr(D | T1): The probability of the data D given theory T1.

• Pr(D | T2): The probability of the data D given theory T2.

If Pr(D | T1) > Pr(D | T2), then T1 better predicts or renders D more probable than T2 does. Under certain Bayesian frameworks, this justifies updating one’s credence in T1 relative to T2. The more D confirms T1 over T2, the more rational it is to prefer T1.

In Bayesian terms, the likelihood of the data under each theory is compared, and this comparison informs our posterior credence in each theory, given the data. The formal apparatus of Bayesian confirmation theory thus provides a precise model of the epistemic force of explanatory arguments. However, even without full Bayesian machinery, the intuitive idea remains the same: theories that make the data unsurprising are to be preferred.

Explanatory Inference and Philosophical Methodology

Explanatory arguments differ from deductive arguments in important ways. In a deductive argument, if the premises are true, the conclusion must be true. In contrast, explanatory arguments are ampliative: they go beyond what is strictly entailed by the premises. This means they are defeasible — open to revision in light of new evidence or better explanations.

Some philosophers are wary of explanatory arguments precisely because of their ampliative nature. They worry that in the absence of empirical tests, explanatory reasoning may be little more than an expression of one’s theoretical preferences. Others embrace explanatory arguments as the only viable way to adjudicate between competing views in domains where deduction is impossible and empirical access is limited.

In many cases, philosophical progress seems to depend on the strength of explanatory reasoning. Consider debates about the metaphysics of time. Should we accept the A-theory, according to which time flows and the present is metaphysically privileged? Or the B-theory, according to which all times are equally real and temporal becoming is illusory? The choice often turns on which theory better explains our temporal experiences, our linguistic practices, or our intuitions about change.

Or consider moral realism. Do moral facts exist independently of our beliefs and attitudes? Realists often argue that moral realism better explains our shared moral judgments and the possibility of moral disagreement. Anti-realists, in contrast, argue that evolutionary and cultural factors suffice to explain our moral beliefs, rendering the appeal to independent moral facts explanatorily superfluous.

In such debates, explanatory arguments are not optional add-ons; they are the main instruments by which philosophers attempt to make progress.

General Strategies for Resisting Explanatory Arguments

Explanatory arguments can be persuasive, even compelling. But like all forms of ampliative reasoning, they are open to critical scrutiny. Their premises are rarely self-evident, and their conclusions are never logically guaranteed. In this section, I examine the primary strategies available for resisting explanatory arguments. These strategies can be used individually or in combination, and they apply across a broad range of philosophical contexts.

We begin with the five strategies outlined in the original version of this paper and then proceed to consider additional resistance strategies drawn from the broader philosophical literature. Each strategy targets a different premise or assumption in the structure of the explanatory argument.

Strategy 1: Denying the Data (D)

The simplest way to resist an explanatory argument is to reject the existence or characterization of the datum to be explained. If there is no data D, then no explanation is needed — and the argument fails at step one.

Illustrative Cases:

• In the fine-tuning argument, one might argue that the appearance of fine-tuning is an illusion, resting on flawed probabilistic reasoning or anthropic bias.

• In consciousness debates, illusionists argue that qualia — as traditionally conceived — do not exist; our sense that they do is a cognitive error.

• In moral realism debates, an error theorist may deny that there are any true moral beliefs to be explained.

This strategy is dialectically powerful when the datum is controversial, poorly defined, or dependent on questionable intuitions.

Strategy 2: Denying the Surprise under T2

Another common strategy is to argue that the data are not surprising or improbable under the rival theory (T2). This is an attack on premise 3 of the explanatory schema: that D is unlikely under T2.

Illustrative Cases:

• For example, philosophers often debate whether the laws of nature merely describe regularities (Humean view) or whether they govern reality in a robust sense (anti-Humean view).Anti Humeans arge that the fact that universe exhibits stable, law-like regularities is better explained by anti Humeanism and is surprising under Humeanism. Humeans may argue that regularities in nature are expected under a best-system account of laws, and so the world’s apparent order is not surprising.

Strategy 3: Denying the Expectation under T1

One might also resist explanatory arguments by arguing that the favored theory (T1) does not, in fact, render D likely or expected. This undermines premise 4.

Illustrative Cases:

• Critics of theism may argue that theism does not predict fine-tuning, since God could have chosen to create life in any number of ways — or not at all.

• Dualists may be pressed on whether their theories really explain consciousness, or whether they simply assume it.

This strategy challenges the explanatory power of T1 and forces its defenders to articulate how, precisely, T1 makes D intelligible. If T1 merely accommodates D without predicting it, its explanatory advantage may be exaggerated.

Strategy 4: Denying that All Else Is Equal

Explanatory arguments conclude that T1 is to be preferred all else being equal. But what if all else is not equal?

In this response, the objector may accept the premises of the argument and the conclusion that, all else being equal, T1 should be preferred over T2. However, they argue that all else is not equal because there exists additional data, D*, which, when considered alongside D, is better explained by T2 than T1. For example, in fine-tuning arguments, naturalists might concede that general facts about fine-tuning support theism but argue that more specific facts about fine-tuning, when combined with the general facts, are better explained under naturalism. If true, this response would show that fine-tuning arguments fail to establish the existence of God.

Strategy 5: Moorean Response

Named after G. E. Moore’s strategy of rejecting premises that lead to implausible conclusions, the Moorean response to explanatory arguments denies the conclusion of the argument and infers that at least one premise must be false.

Rather than identifying a specific premise of the argument as false, the responder argues that there are stronger reasons to reject the conclusion than to accept the conjunction of the premises. Thus, the conjunction of the premises must be false. For example, in the case of fine-tuning arguments, a non-theist might argue that there are strong independent reasons to deny the existence of God, and these reasons outweigh the justification for accepting the premises of the fine-tuning argument. Therefore, we ought to reject the premises rather than accept the conclusion.

Strategy 6: Undermining the Inference Norm (Anti-IBE Skepticism)

A more radical line of resistance challenges the very idea that explanatory power is a reliable guide to truth — especially in metaphysics and normative domains.

Core Idea:

Inference to the best explanation (IBE) may be a good heuristic in empirical science, but it is unreliable when applied to domains with no empirical feedback mechanisms (e.g., modality, ethics, consciousness).

Illustrative Cases:

• One might argue that positing unobservable entities or metaphysical laws solely on the basis of explanatory power is methodologically suspect.

• Some philosophers of mathematics resist Platonism even if it explains objectivity and necessity well, because the inference to abstracta is too metaphysically extravagant.

This strategy challenges the epistemic normativity of IBE itself. It is a higher-order objection — not to any particular argument, but to the general method of explanatory reasoning in philosophy. Its power depends on how skeptical one is about metaphysical inference.

Conclusion

Explanatory arguments are central to philosophical practice. From the metaphysics of modality to the nature of consciousness, from the objectivity of morality to the design of the universe, philosophers routinely appeal to explanation in their attempts to make sense of complex and often abstract phenomena. This mode of reasoning — inference to the best explanation — is not merely a stylistic preference; it often plays a decisive role in theory choice, especially in domains where empirical adjudication is limited or unavailable.

Throughout this article, we have examined the core structure of explanatory arguments. These arguments begin with a datum in need of explanation, evaluate how well competing theories account for that datum, and conclude — all else being equal — that the theory which better explains the data ought to be preferred. This schema is deceptively simple, yet remarkably powerful. It allows philosophers to compare rival theories, articulate explanatory virtues (such as scope, simplicity, and depth), and make plausible inferences about which metaphysical or normative frameworks are most likely to be true.

We have also seen, however, that explanatory arguments are vulnerable to a wide range of objections. A defender of a rival theory can challenge any step in the argument: deny the data, deny its surprisingness under the competing theory, deny that the favored theory really explains it, argue that all else is not equal, or simply reject the conclusion on Moorean grounds.

Despite these vulnerabilities, explanatory arguments remain indispensable. In many areas of philosophy. Philosophical inquiry often deals with questions that extend beyond the reach of empirical confirmation, and in such cases, explanatory power is one of the few epistemic tools we have. If philosophy is to proceed at all, it must make use of arguments that, though defeasible, allow us to reason about what the world is like on the basis of what best explains what we observe, experience, or understand.

Yet the limitations of explanatory arguments must also be acknowledged. They are not deductively valid, and their conclusions are always open to revision. They depend on judgments about probability, simplicity, coherence, and plausibility — judgments that are often shaped by background beliefs, theoretical commitments, and cognitive biases. Philosophers who deploy explanatory arguments must therefore proceed with care. They must be explicit about their assumptions, transparent about their inferential commitments, and humble about the strength of their conclusions.

In sum, explanatory arguments are powerful but fallible tools in the philosophical toolbox. They enable us to reason about what lies behind the phenomena we encounter, to navigate between competing worldviews, and to make principled choices between rival theories. But they also demand critical scrutiny — both of the arguments themselves and of the methods by which they are constructed and assessed. If philosophy is, at its core, a discipline of reasoned inquiry into the fundamental structure of reality, then explanatory arguments are — and will remain — at the heart of that endeavor.