Contradiction (L. contra-, “against” + dicere, “to speak”) is the condition of conflict in speech.

There are two kinds of contradiction, material contradiction and immaterial contradiction.

Contradiction is material (L. materies, “wood, timber”) when it exists as an attribute of language, usually but not always in a physical object, as in a work of literature.

Contradiction is immaterial (L. in, “not” + materies) when it exists apart from language; such that a contradiction would exist if immaterial ideas were put into language.

Since contradiction, by definition, can only describe speech, one can think of material contradiction as actual – it is “to speak against” literally – and immaterial contradiction as potential – “to speak against” figuratively.

Of the immaterial kind of contradiction, there are three classes – social, psychic, and phenomenal. Contradiction in society is divergence; contradiction in psyche is ambivalence; contradiction in phenomena is over-determination.

A social (L. societas, “partnership for a common purpose”) contradiction occurs when there is an ethical conflict between the various partners of an organization that is united for a common purpose. When addressing social contradiction, a spectrum of consistency (L. com, “together” + stare, “to stand”) can be plotted on a line measuring how well the partners of a society stand together, ranging from consistency to inconsistency to divergence.

A society is consistent when its partners stand together. A society is inconsistent when its partners do not stand together. A society is divergent (L. di, “in twain” + vergere, “to bend, turn”) when its partners not only stand apart but also move away from each other.

A psychic (Gk. psykhe, “breath, spirit, soul”) contradiction occurs when there is an emotional conflict between the various thoughts of a mind that ought to be able to resolve a given dilemma by way of agreement and disagreement. When addressing psychic contradiction, a spectrum of certainty (L. cernere “to sift, separate”) can be plotted on a line measuring how well a mind can separate its thoughts on a dilema, ranging from certainty to uncertainty to ambivalence.

A psyche is certain when the mind can separate its thoughts on an issue and assert its endorsement of a given position. A psyche is uncertain when the mind cannot separate its thoughts on an issue, such that it cannot assert its endorsement of a given position. A psyche is ambivalent (L. ambi-, “on both sides” + valere, “to be strong”) when the mind can separate its thoughts on an issue and yet it cannot assert its endorsement of a given position because it is compelled by multiple positions that are nevertheless mutually exclusive.

A phenomenal (Gk. phainein, “to show”) contradiction occurs when there is a rational conflict between the various interpretations of a material’s intent. When addressing phenomenal contradiction, a spectrum of determination (de-, “completely” + terminare, “to end”) can be plotted on a line measuring how comfortable someone feels bringing the interpretation of a material to an end, ranging from determinate to indeterminate to over-determined.

A material is determinate when the interpretation of its intended meaning can reasonably be brought to an end. A material is indeterminate when the interpretation of its intended meaning cannot reasonably be brought to an end. A material is over-determined (OE. ofer-, “surpassing” + L. de-, “completely” + terminare, “to end”) when the interpretation of its intended meaning can be responsibly brought to multiple ends that are equally compelling yet mutually exclusive.

Of the material kind of contradiction, there are two classes – legal contradiction and philosophical contradiction.

A legal (L. lex, “law”) contradiction is a statement from a speaker that is in conflict with a statement from another speaker. Someone says something, and then someone else says something against the first statement. The purpose of contradiction in law is to gather multiple statements on an issue in order to decide which one is the most accurate. In law, contradiction is a good thing.

A philosophical (Gk. philo “loving” + sophia “knowledge, wisdom”) contradiction is a statement from a speaker that is in conflict with an earlier statement from that same speaker. Someone says something, and then that person says something else against the first statement. The purpose of contradiction in philosophy is to recognize when a statement on an issue is logically invalid. In philosophy, contradiction is not a good thing.

The goal of a legal contradiction is to completely avoid philosophical contradiction, and a statement found to be philosophically contradictory could never serve as a serious legal contradiction. The goal of a legal contradiction is to produce a valid statement (even is it is not ultimately sound); the fact of a philosophical contradiction is that it is invalid. In this sense, legal and philosophical contradiction are polar opposites.

Validity (L. valere, “to be strong”) is a measure of the logical strength of a statement, which is the degree to which tha statement’s conclusions follow from its premises. When addressing material contradiction, a spectrum of validity can be plotted on a line measuring the logical unity of a statement, ranging from legal contradiction to philosophical contradiction – from a total validity to a total non-validity.

A minor form of philosophical contradiction, an incongruity (L. in, “not” + com, “with” + gruere “fall”) is a statement that does not fall together with a speaker’s other statements. (The comparable form of legal contradiction is congruity [L. com, “with” + gruere “fall”], or the ability of a speaker’s statements to fall together.)

Another minor form of philosophical contradiction, a discrepancy (dis, “in twain” + crepare, “to rattle, crack”) is a statement that sounds unpleasant against the other statements of a speaker. (The comparable form of legal contradiction is harmony [Gk. harmos, “joint, shoulder”], or the pleasant-sounding conjunction of all the statements of a speaker.)

A moderate form of philosophical contradiction, a paradox (para, “contrary to” + doxa, “opinion”) is a statement that at first seems contradictory but which is in fact not contradictory upon further reflection, which means that the statement arises contrary to both the expectation of the audience and the opinion of the speaker. (The comparable form of legal contradiction is an assertion [ad, “to” + serere “join”], or a straight-forward statement joining one’s self to a particular fact or belief.)

Another moderate form of philosophical contradiction, a dialectic (Gk. dia, “across, between” + legein “speech”) is an articulation of opposing statements for the sake of reasoning between the conflicting views and resolving an issue. (The comparable form of legal contradiction is a manifesto [L. manus, “hand” + festus “able to be seized”], or a list of assertions that one can easily grasp from another.)

Another moderate form of philosophical contradiction, antitheses (Gk. anti “against” + tithenai, “to place”) are an articulation of opposing statements placed against each other without the impulse to resolve the issue. (The comparable form of legal contradiction is a thesis [Gk. tithenai, “to place”], or a statement placed forth as a truth-claim to be evaluated.)

A severe from of philosophical contradiction, ambiguity (L. ambi-, “on both sides” + agree, “to drive) is a statement that drives both sides of an issue, thus exhibiting the potential to be understood in two or more different ways. (The comparable form of legal contradiction is argumentation [L. arguere, “to make clear, demonstrate”], or a statement compelling an audience to adopt a given position by clearly demonstrating its preferability.)

Another severe form of philosophical contradiction, antinomy (Gk. anti, “against” + nomos, “law”) is a statement that articulates two or more laws that clash against each other without the impulse to privilege one over the other. (The comparable form of legal contradiction is a proof [L. probus, “worthy, good, upright, virtuous,"], or a statement that systematically establishes the truth of a position.)

The most severe form of philosophical contradiction, incommensurability (L. in, “not” + com, “with” + mensurare “to measure”) is the condition of a statement that demonstrates how two or more systems of thought are so fundamentally different that they cannot be addressed in the same terms. (The comparable form of legal contradiction is the systemization [Gk. syn, “together” + histanai, “to set up”], or a statement that sets up altogether a perspective on an issue.

Social contradiction relates to psychic contradiction according to consciousness (L. com, “with” + scire “to know”) – whether a mind is conscious or unconscious of the contradiction, or the lack of it, in society.

Psychic contradiction relates to material contradiction according to intention (L. in “toward” + tendere “to stretch”) – whether the material is intentionally or unintentionally imbued with the contradiction, or the lack of it, of a mind.

Material contradiction relates to phenomenal contradiction according to actuality (L. agere, “to do, set in motion”) – whether an interpreter projects or discovers contradiction, or the lack of it, in the material.