A few words on philosophy are in order at the beginning. Philosophy can roughly be classified into six branches.
- Metaphysics: Examines the nature of reality.
- Epistemology: Examines the nature of knowledge.
- Ethics: Examines the nature of human behaviour.
- Politics: Examines the nature of governance.
- Economics: Examines the nature of goods and services.
- Aesthetics: Examines the nature of beauty.
The study of truth falls into all six branches of philosophy, and has serious consequences in each.
That said, before we can examine truth, we must agree on a few metaphysical premises. Without these premises, truth cannot be established. And if truth cannot be established in principle, there is no point in trying to establish it or fight over it. The five premises are:
- There exists an external reality. This external reality exists independent of an observer.
- In this external reality, somewhere in space and sometime in time, there exists an observer.
- Parts of this external reality are accessible to the observer. Through sensation, perception, and thought the observer may construct an observed reality.
- Through language the observer may construct statements about an observed reality.
- The relationships (match, mismatch) between external reality, an observed reality, and a statement about an observed reality are as follows.
(Note that human language is less specific about agreements between external reality, an observed reality, and a statement about an observed reality, than it is about disagreements. All agreements are called a truth, a fact, or a matter of fact.)
Example: Statements of witnesses to a murder.
External reality: The murderer is a woman.
Observed realities of ...
Alice: The murderer is a woman.
Bob: The murderer is a woman.
Carol: The murderer is a man.
David: The murderer is a man.
Statements of ...
Alice: "The murderer is a woman."
Bob: "The murderer is a man."
Carol: "The murderer is a man."
David: "The murderer is a woman."
Alice and Bob perceive the truth, but only Alice speaks the truth; Bob is lying. Carol and David perceive an illusion. Carol speaks the truth, which is really a falsehood. David is lying and produces an accidental truth.
Of course, there is a lot to be said about partial truths and partial falsehoods, but the point of these premises is to establish a set of basic rules to guarantee that truth can be established in principle.