Impossibility may refer to:

Philosophy and logic

Epistemic impossibility In philosophy and modal logic, epistemic possibility relates a statement under consideration to the current state of our knowledge about the actual world: a statement is said to be: * ''epistemically possible'' if it ''may be true, for all we kno ...

, in modal logic a statement that cannot be true, given what we know *

Subjunctive impossibility Subjunctive possibility (also called alethic possibility) is a form of modality studied in modal logic. Subjunctive possibilities are the sorts of possibilities considered when conceiving counterfactual situations; subjunctive modalities are modal ...

, types of statement that cannot be true based on various types of subjunctive modality **

Logical impossibility Logical possibility refers to a logical proposition that cannot be disproved, using the axioms and rules of a given system of logic. The logical possibility of a proposition will depend upon the system of logic being considered, rather than on the ...

, a statement that contains a logical contradiction *

Impossible world In philosophical logic, the concept of an impossible world (sometimes called a non-normal world) is used to model certain phenomena that cannot be adequately handled using ordinary possible worlds. An impossible world, i, is the same sort of thing ...

, a concept in philosophical logic

Other uses

Impossibility of performance The doctrine of impossibility or impossibility of performance or impossibility of performance of contract is a doctrine in contract law. In contract law, impossibility is an excuse for the nonperformance of duties under a contract, based on ...

, in contract law an excuse for non-performance of a contract *

Impossibility defense An impossibility defense is a criminal defense occasionally used when a defendant is accused of a criminal attempt that failed only because the crime was factually or legally impossible to commit. Factual impossibility is rarely an adequat ...

, a criminal defense for a crime that was legally impossible to commit *

Proof of impossibility In mathematics, an impossibility theorem is a theorem that demonstrates a problem or general set of problems cannot be solved. These are also known as proofs of impossibility, negative proofs, or negative results. Impossibility theorems often reso ...

, in mathematics a proof that demonstrates that a particular problem cannot be solved

Philosophy and logic

Other uses

See also