What is truth?

"...even we knowers of today, we godless anti-metaphysicians, still take our fire, too, from the flame lit by the thousand-year-old faith, the Christian faith which was also Plato's faith, that God is truth; that truth is divine."

- Nietzsche

"Truth" is a trendy topic these days. We seem to give a lot of attention to what is correct, what is wrong, who is correct, who is wrong, as indicated by the increasing use of "fact checking". Yet this is accompanied by claims that the truth can never be determined, or is a matter of personal choice, or that truth is a meaningless concept or simply does not exist. How do we make sense of these claims? What is truth, anyway? That is what we want to discuss.

The meaning of "truth" has been a topic for philosophers since ancient times. As truth is supposed to tell us something about what is, the choice of theory is highly dependent, and affects, what we believe in fact is - that is, metaphysics. Disagreements about "truth" often come from fundamental disagreements about the types of entities that truth is meant to describe.

Theories of truth have been grouped into four general categories:

Correspondence theories state that a proposition is true if it corresponds to a fact. If there is no such fact, the proposition is false. "The cat is on the mat" is true if this corresponds to the fact that the cat is indeed on the mat. This seems to be the most intuitive meaning, and dates to Aristotle's "to say of what is that it is, or of what is not that it is not, is true." This seems to imply that there are facts "out there" that exist independently of the believer. Correspondence theories are generally associated with "realism", the claim that entities exist and that their existence and properties are independent of our languages, conceptual schemes, etc.

Coherence theories, in contrast, are based on anti-realism or idealism, the view that the world as we experience it is irreducibly connected with the ways we observe, conceptualise and communicate. We have limited and undefined access to the "world as it is", if such an entity exists. As each proposition can only be evaluated based on the prior evaluation of other propositions, all we can hope to find is a system of propositions that form a coherent (singular) truth. A proposition is then true if it is part of this coherent truth, that is, it is coherent with the other propositions in this truth.

Pragmatist theories were developed by William James, Charles Sanders Peirce and others to bring practical matters such as experience, belief and doubt into the discussion. This included a focus on what types of inquiries were possible and what could be verified.

Peirce defined "truth" as that which "endless investigation would tend to bring scientific belief", explicitly excluding propositions that are incapable of being evaluated. Although truth can only be determined at the end of science, a true proposition will never conflict with subsequent experiences. This does not necessarily conflict with correspondence theories or coherence theories.

Deflationary theories state that all such discussions are meaningless distractions. Is there a difference between saying "It is true that the cat is on the mat" and "The cat is on the mat"? Why do we need to have a concept of "truth" as an abstract entity?

Epistemology

Is knowledge knowable? If not, how do we know this?

- Woody Allen

Especially for the pragmatists, the meaning of truth is tied up with questions of how we determine what is true. Again, it is helpful to categorise various positions.

Rationalists such as Plato focused on the power of intellect to know or discover truths. For Plato, the fundamental entities were abstract "forms" such as"redness", "beauty" and "truth". The objects that we interact with - the people, animals, rocks, trees, etc. - are only a pale reflection of these underlying primary forms. As a result, our experiences are poor sources of knowledge. This focus on intellect continued through philosophy, such as Descartes's belief that his simple awareness of his own thoughts could provide the foundation for his philosophical system. Idealist philosophers would argue that our thinking is all that exists.

In contrast, empiricists believe that experience was our only source of knowledge. This does not mean that we can have empirical knowledge - there maybe be some topics, like the nature of causality, where empirical knowledge is impossible. In these cases, any knowledge would be impossible.

Of course, we can also be sceptics, doubting our ability to obtain knowledge. We cannot even say with certainty that we cannot gain knowledge; all we can do is withhold judgements of everything, including whether our scepticism is justified.

Kant, with his transcendental idealism, developed an integration of intellect, observation and scepticism that formed the structure for much further work in this area. characterisations that provide knowledge independent of experience.

Science and truth

Science is often credited as forming the most reliable approach towards truth. Science is often described as based on induction. A white swan, another white swan, another white swan... It seems that all swans are white. But as many have pointed out, this is a rather unreliable method for discovering truth. Popper made important advances in our understanding of science, claiming that it is based on formulating hypotheses that are then tested to see if they can be disproven. If a hypothesis provides a prediction that is later shown to be wrong, we discard the hypothesis. If it yields a correct prediction, we might have increased belief in the hypothesis, but our belief is always tentative, capable of being overturned by the next tested prediction.

This captures the provisional nature of truth in science, but has problems:

• Almost all major hypotheses are known to provide false predictions when they are born, developed, and built upon. Darwin knew his theory of evolution could not work. Newton knew his theory of light was incompatible with the existence of mirrors. If we discarded theories because they yielded wrong predictions, science could not proceed.
• The falsification of a hypothesis relies on positive claims about what we are testing. We must believe that our experiments are measuring what we want them to measure, and that our analysis is done correctly. If nothing can ever be proven, then nothing can ever be disproven.

For a discussion of the history of the scientific method: Just Use Your Thinking Pump