Semantic Realism vs. Anti-Realism: Truth and Meaning

1. The Realism/Anti-Realism Landscape

The terms 'realism' and 'anti-realism' are used to describe a wide variety of philosophical positions. Before we zero in on the specific semantic debate that is our focus, it's helpful to understand the broader context.

Let's start with a video that explores some of the main ways these terms are used.

As the video highlights, the most philosophically deep version of this debate isn't just about whether certain things exist, but about whether reality itself is independent of our minds and our methods of inquiry.

• A realist (in this deep sense) believes that reality is what it is, regardless of what we can know or prove about it.
• An anti-realist believes that reality is, in some fundamental way, shaped by or dependent on our cognitive abilities and practices.

For a mathematical mind, the example of the Twin Prime Conjecture is telling. The realist asserts it's either true or false right now, even if we never find a proof. The anti-realist suggests that if it's fundamentally unprovable and undisprovable, it's neither true nor false—because mathematical truth doesn't exist in a realm beyond our (ideal) capacity for proof.

2. Dummett's Reframing: From Metaphysics to Meaning

The British philosopher Michael Dummett (1925-2011) famously argued that these traditional metaphysical debates are best understood and resolved as debates in the philosophy of language—specifically, debates about the correct theory of meaning. This move is what gives us the semantic version of the realism/anti-realism debate.

The core idea is this: instead of arguing about a "mind-independent reality" directly, we should ask what it is we know when we understand the meaning of our sentences. The answer to this question, Dummett argued, will determine which metaphysical picture is coherent.

The following reading from an overview of Dummett's work explains this crucial shift and defines the two opposing positions.

This reading introduces the central contrast that you must master for this lesson's learning outcome. Let's summarize the two positions:

Semantic Realism

• Theory of Meaning: Meaning is given by truth-conditions. To understand a sentence is to know what the world would have to be like for the sentence to be true. This is often called a truth-conditional theory of meaning.
• Theory of Truth: Truth is potentially verification-transcendent. A statement can be true or false even if we have no way of ever finding out which it is. Truth is a matter of correspondence to a mind-independent reality.
• Key Principle: Because every statement's truth-condition either obtains or does not obtain in reality, the realist accepts the Principle of Bivalence: every statement is determinately either true or false.

Semantic Anti-Realism

• Theory of Meaning: Meaning is given by assertability-conditions (or verification-conditions). To understand a sentence is to know what counts as evidence or a justification for asserting it. This is often called a verificationist theory of meaning.
• Theory of Truth: Truth is epistemically constrained. Truth cannot outrun our (in-principle) ability to know it. To be true is to be knowable, or justifiably assertable. The idea of a truth we could never have evidence for is rejected as incoherent.
• Key Principle: For statements that are undecidable (where we can in principle neither verify nor falsify them), the anti-realist rejects the Principle of Bivalence. Such statements are considered neither true nor false.

3. Articulating the Positions

Now let's hear these ideas articulated by Dummett himself. In this interview, he first explains the realist theory of meaning developed by the logician Gottlob Frege, which is the classic example of a truth-conditional theory. He then contrasts this with his own anti-realist view.

Dummett’s central argument against realism, which we'll explore more later, is that we couldn't possibly learn or manifest our understanding of these verification-transcendent truth-conditions. How could you show someone that you grasp what it means for a statement to be true, if that truth is, by definition, beyond any possible evidence? For the anti-realist, meaning must be tied to our public practices of justification and proof.

4. A Concrete Example and the Impact on Logic

Let's apply this to a familiar case from mathematics. Consider the Goldbach Conjecture:

"Every even integer greater than 2 is the sum of two primes."

As you know, this is currently unproven.

• The semantic realist says: The conjecture is either true or false, right now. There is a fact of the matter, resident in the structure of the mathematical universe, even if we never discover it. We understand the sentence because we grasp the condition under which it would be true (that this property holds for all even integers) and the condition under which it would be false (that there exists a counterexample).

• The semantic anti-realist says: We understand the conjecture by knowing what would count as a proof of it or what would count as a refutation (a counterexample). If the conjecture turns out to be undecidable in principle, then it is neither true nor false. It would be meaningless to talk of its truth or falsity if it lies beyond any possible demonstration.

This has profound consequences for logic. The anti-realist's rejection of bivalence for undecidable statements leads to a rejection of the corresponding logical law, the Law of Excluded Middle ($P\vee \neg P$). If a statement $A$ is undecidable, the anti-realist cannot assert $A$ and cannot assert $\neg A$. Following a verificationist semantics, you can only assert a disjunction '$A\vee B$' if you can assert $A$ or you can assert $B$. Therefore, the anti-realist cannot assert '$A\vee \neg A$'.

This is precisely the move made by intuitionistic logic, which you may have encountered in your mathematical logic studies. The philosophical debate between realism and anti-realism thus provides a deep justification for the technical divergence between classical and intuitionistic logic.

For a final, concise summary of how these ideas relate, you can consult the Internet Encyclopedia of Philosophy's article on the Semantic Theory of Truth. Section 5, subsection (8), directly discusses the realism/anti-realism debate, framing it as a choice between two equations:

• Realism: MS = TC (Meaning of a Sentence = Truth-Conditions)
• Anti-realism: MS = AC (Meaning of a Sentence = Assertibility-Conditions)

Conclusion

Today we have unpacked the complex and far-reaching debate between semantic realism and anti-realism. This is not just a technical dispute; it's a clash of fundamental pictures about the relationship between mind, language, and reality.

Key Takeaways:

• Semantic Realism holds that the meaning of a sentence is its truth-condition, which can be true or false independently of our ability to know it (verification-transcendent truth). This view supports the universal application of the Principle of Bivalence.
• Semantic Anti-Realism holds that the meaning of a sentence is its assertability-condition (or method of verification). Truth is epistemically constrained and cannot in principle outrun our evidence. This view entails rejecting the Principle of Bivalence for undecidable statements.
• This philosophical debate provides the motivation for a choice between different logical systems, such as classical logic (favored by realists) and intuitionistic logic (favored by anti-realists).

Preview of the Next Lesson:

The debate we've examined hinges on the nature of truth. Both the realist's verification-transcendent truth and the anti-realist's epistemically constrained truth are different conceptions of the same property. In the next lesson, we will examine the leading philosophical theories of truth—correspondence, coherence, and deflationary theories—to better understand the foundations on which the realist and anti-realist build their respective worldviews.