Truth: Reality, Statements, and Criteria
Item 4: Problems Around the Truth
1. The Theory of Truth
1.1 The Truth Term
The word “truth” encompasses various uses and meanings, from authenticity to the opposite of false or wrong. The term has three generic applications:
- Ethical (truth and moral propriety)
- Ontological (truth as a property of reality)
- Epistemological (truth as the property of knowledge’s accuracy)
1.2 Truth as a Property of Reality
In Greek, “truth” (aletheia) signifies the unveiling of what is hidden—the essence of things. Classical philosophers viewed truth as the inherent nature of things.
- Parmenides: Being and thinking are one and the same.
- Plato: The world of Ideas is the true reality.
Truth (reality) cannot be merely what appears to us, as “material reality” constantly changes and is thus only a semblance of the true reality. True reality remains stable and is knowable only through reason.
Scholastic philosophy linked truth to doctrine, asserting that only God is truth and divine Ideas (those within God’s mind) are truly real. Metaphysical truth is the alignment of things with the divine.
1.3 Truth as a Property of Statements
Greeks and Scholastics also held an epistemological view of truth. The true or false pertains to what is affirmed or denied about things—what is said. Truth is not a property of reality itself, but of statements about it.
Aristotle, whose definition was further developed by Thomas Aquinas, defined truth as the correspondence between the object and understanding—the overlap between what is said and the facts. This led to Tarski’s correspondence theory.
1.3.1 Truth as Correspondence
Aristotle (Metaphysics) stated that telling the truth means affirming what is united and denying what is separated (a precursor to the correspondence theory).
The correspondence theory posits that a statement is true if its description matches the facts as we know them. It has two forms:
- Strong: Identity or equality between what is and what is stated.
- Flexible: A relationship between the statement and our knowledge of the facts.
Knowing the facts implies some truth in what is known: a statement is true if it corresponds to what we know to be true. However, some true statements don’t correspond to any fact, as they don’t describe anything (e.g., “I read or I do not read”—a logical truth). These and other objections led to alternative theories.
1.3.2 Semantic Theory of Truth
Alfred Tarski proposed the “semantic theory” to describe a conception of truth that is materially adequate and formally correct, aiming for a definition that avoids contradictions arising in traditional definitions.
Tarski viewed truth as a property of statements, definable in semantic terms: a proposition “p” is true if and only if what it signifies occurs in reality. He distinguished between the use of terms (attributing a property to an entity) and the mention of terms (attributing a property to the name, not the entity).
This distinction leads to two language levels: object language (using terms to discuss facts) and metalanguage (referring to language itself).
A definition of truth is “adequate” if, for all cases where “X” is the name of a proposition and “p” is the proposition itself, there is “formal equivalence” (T).
1.3.3 Pragmatic Theory of Truth
Pierce and William James argued that a proposition is true (or believed to be true) if it is practically useful and accepted as true by anyone sufficiently informed about it.
1.3.4 Theory of Consensus
Habermas posited that truth is not just a property of a statement but an “ideal requirement” demanding universal assent after all relevant arguments are presented. Thus, “Socrates was Athenian” would be true once universally accepted.
2. The Real Content of Statements
2.1 Truths of Reason and Truths of Fact
Statements like “A = A”, “the sum of a triangle’s internal angles is 180 degrees”, “the sun will rise tomorrow”, or “Socrates was Athenian” are generally accepted as true. However, their content falls into two distinct categories: some refer to ideal properties or relations between subject and predicate, while others refer to facts of experience.
Leibniz distinguished between truths of reason (necessary, their opposite impossible) and truths of fact (contingent, their opposite possible).
2.2 Relations of Ideas and Relations of Facts
Hume differentiated between these two types of relations. Relations of ideas belong to science, geometry, algebra, arithmetic, and any intuitively or demonstrably certain affirmation. These propositions are discoverable through thought alone.
Relations of facts belong to natural sciences, based on experience. Contrary assertions are often possible, as they don’t imply contradiction and are conceivable even if not absolutely true. For Hume, only relations of ideas are truly certain, while matters of fact are merely possible.
2.3 Formal Truth and Empirical Truth
Formal truth (logical truth) is the absence of contradiction between terms, found in mathematical and logical statements demonstrable through their rules.
Empirical truth is the match, agreement, or correspondence between a statement and reality, verifiable only through experience. Only particular statements can be verified, not universal ones, which are only probabilistically assertable.
3. The Criteria of Truth
3.1 Degrees of Certainty
- Ignorance: Lack of knowledge.
- Opinion: A belief held with the possibility of being wrong.
- Doubt: Suspension of judgment.
- Certainty: Confidence in a statement’s truth.
3.2 Criteria of Truth
A criterion of truth is a property of a sentence that allows us to know with certainty whether it’s true or false.
- Tradition: What has long been considered true by a community.
- Authority: Acceptance based on the source’s credibility.
- Verifiability: Agreement with reality.
- Logical coherence: Derivation from axioms without contradiction within the system (applicable to formal sciences).
- Utility: Usefulness in orienting people in reality.
- Evidence: The most important criterion. The evident is indisputable and must be accepted once understood, often intuitive but sometimes demonstrable.