This is a list of some of the major problems in philosophy. Meta-philosophy Meta (from the Greek μετά, meta, meaning "after" or "beyond") is a prefix meaning "more comprehensive" or "transcending". In modern nomenclature, meta- can also serve as a prefix meaning self-referential, as a field of study or endeavor (metatheory: theory about a theory; metamathematics: mathematical theories about mathematics; meta-axiomatics or meta-axiomaticity: axioms about axiomatic systems; and that meta-Semantics is the study about reference to meaning and meaning to reference. The term can be used to refer to subfields of several distinct disciplines, including philosophy, linguistics and science. Philosophy of language Counterfactuals A counterfactual statement is a conditional statement with a false antecedent. For example, the statement "If Joseph Swan had not invented the modern incandescent light bulb, then someone else would have invented it anyway" is a counterfactual, because in fact, Joseph Swan invented the modern incandescent light bulb. The most immediate task concerning counterfactuals is that of explaining their truth-conditions. As a start, one might assert that background information is assumed when stating and interpreting counterfactual conditionals and that this background information is just every true statement about the world as it is (pre-counterfactual). In the case of the Swan statement, we have certain trends in the history of technology, the utility of artificial light, the discovery of electricity, and so on. We quickly encounter an error with this initial account: among the true statements will be "Joseph Swan did invent the modern incandescent light bulb." From the conjunction of this statement (call it "S") and the antecedent of the counterfactual ("¬S"), we can derive any conclusion, and we have the unwelcome result that any statement follows from any counterfactual (see the principle of explosion). Nelson Goodman takes up this and related issues in his seminal Fact, Fiction, and Forecast; and David Lewis's influential articulation of possible world theory is popularly applied in efforts to solve it. Epistemology Gettier problem Plato suggests, in his Theaetetus (210a) and Meno (97a–98b), that "knowledge" may be defined as justified true belief. For over two millennia, this definition of knowledge was accepted by subsequent philosophers. An item of information's justifiability, truth, and belief were seen as the necessary and sufficient conditions for knowledge. But in 1963, Edmund Gettier published an article in the journal Analysis, a peer-reviewed academic journal of philosophy, entitled "Is Justified True Belief Knowledge?" which offered instances of