Knowledge, Truth, and Meaning

An excerpt from the online hypertext Human Knowledge: Foundations and Limits.

Knowledge

Knowledge is justified true belief. Belief in a proposition p is justified if 1) it is developed though a process that reliably yields truth, 2) it is appropriately caused by the fact that p is true, and 3) it would generally not be held if p were false. The reliability criterion entails that synthetic (i.e. inductive) knowledge is always provisional. The causal and counterfactual criteria entail that whether a true belief counts as knowledge depends on inherently imprecise judgments concerning whether the believer is accidentally right. Operationally, a belief is justified if and only if it is convincing and defensible.

Truth

Truth is logical and parsimonious consistency with evidence and with other truth. Evidence is any and all perceived circumstances.

The Principle of Parsimony (or Occam's Razor) is that the simpler of two explanations is to be preferred when they are otherwise equivalent.

Humans have proposed several criteria for truth.

The Correspondence Theory of Truth is that the terms of true propositions map to elements of reality in a way that validates the proposition.
The Coherence Theory of Truth is that true propositions are those in the system of mutually coherent propositions that is more complete than any rival system.
The Pragmatic Theory of Truth is that true propositions are those that are most useful to believe and that are thus "fated to be ultimately agreed to by all who investigate".

The Correspondence Theory begs the question by assuming that reality can be known directly and certainly. Depending on the meaning of 'complete', the Coherence Theory either reduces to the Correspondence Theory, or it makes truth a purely social (or divine) construct. The Pragmatic Theory either underdetermines the truth of certain propositions, or it reduces to a variant of the social version of the Coherence Theory. The proper notion of truth is coherence grounded in correspondence.

Origins of Knowledge

Propositions can classified according to the dependence of their truth value on their terms:

Analytic propositions are those whose truth value can be deduced from only the definitions of their terms.
Synthetic propositions are those whose truth value cannot be deduced from only the definitions of their terms.

Epistemic Provisionality. All synthetic propositions (including this one) can only be known from experience and are subject to doubt. It is logically possible that all experience is deceptive and that the world is illusory. The only absolutely certain truths are true analytic propositions and the synthetic proposition that something exists.

Cogito Ergo Sum. Descartes argued "I think, therefore I am". However, "I" could be illusory, and the fact of my thinking only warrants the certainty that something exists: cogito ergo est.

Meaning

The denotation (or extension) of a term is the set of entities it refers to. The connotation (or intension) of a term is the properties and concept(s) associated with it.

The meaning of a term is the context-sensitive connotation ultimately established by its relevant denotation and use.

The Verifiability Principle holds that a statement is propositionally meaningless (i.e. states no proposition) if it is neither logically decidable nor empirically verifiable. Positivism is a stricter form of Empiricism that asserts the Verifiability Principle.

Theories of Meaning

Humans have proposed three sorts of explanation for meaning:

The Referential Theory of Meaning is that the meaning of a term is the things in the world it refers to.
The Conceptual Theory of Meaning is that the meaning of a term is the properties and concepts associated with it.
The Behavioral Theory of Meaning is that the meaning of a term consists of the behaviors and dispositions associated with it.

The Referential Theory is confounded by terms that have the same referent but different meaning, such as 'morning star' and 'evening star'. The Conceptual Theory reduces to dictionary-like circularity for many concepts that can only be described by the word(s) to which they help give meaning. The Behavioral Theory is undermined by behaviors and dispositions that underspecify the meanings they are supposed to impart.

Theories of Knowledge

Humans fall into two camps depending on whether they believe synthetic a priori knowledge is possible:

Rationalism is the thesis that some synthetic propositions can be known from reason alone and independent of any experience.
Empiricism is the thesis that all synthetic propositions can only be known from experience.

Rationalism incorrectly assumes that existence arranges for reason to discover the nature of reality through introspection alone.