Cum Hoc Ergo Propter Hoc. The counter assumption, that correlation proves causation, is considered a questionable cause logical fallacy in that two events occurring together are taken to have a cause-and-effect relationship. This fallacy is also known as cum hoc ergo propter hoc, Latin for "with this, therefore because of this", and "false cause". A similar fallacy, that an event that follows another was necessarily a consequence of the first event, is sometimes described as post hoc ergo propter hoc (Latin for "after this, therefore because of this").
As with any logical fallacy, identifying that the reasoning behind an argument is flawed does not imply that the resulting conclusion is false. In the instance above, if the trials had found that hormone replacement therapy caused a decrease in coronary heart disease, but not to the degree suggested by the epidemiological studies, the assumption of causality would have been correct, although the logic behind the assumption would still have been flawed. Usage[edit] Post Hoc Ergo Propter Hoc.
Post hoc ergo propter hoc (Latin: "after this, therefore because of this") is a logical fallacy (of the questionable cause variety) that states "Since event Y followed event X, event Y must have been caused by event X. " It is often shortened to simply post hoc. It is subtly different from the fallacy cum hoc ergo propter hoc (correlation does not imply causation), in which two things or events occur simultaneously or the chronological ordering is insignificant or unknown. Post hoc is a particularly tempting error because temporal sequence appears to be integral to causality.
The fallacy lies in coming to a conclusion based solely on the order of events, rather than taking into account other factors that might rule out the connection. Pattern[edit] The form of the post hoc fallacy can be expressed as follows: A occurred, then B occurred.Therefore, A caused B. When B is undesirable, this pattern is often extended in reverse: Avoiding A will prevent B. Examples[edit] In popular culture[edit] Law of Thought. The laws of thought are fundamental axiomatic rules upon which rational discourse itself is often considered to be based. The formulation and clarification of such rules have a long tradition in the history of philosophy and logic.
Generally they are taken as laws that guide and underlie everyone's thinking, thoughts, expressions, discussions, etc. According to the 1999 Cambridge Dictionary of Philosophy,[1] laws of thought are laws by which or in accordance with which valid thought proceeds, or that justify valid inference, or to which all valid deduction is reducible. Laws of thought are rules that apply without exception to any subject matter of thought, etc.; sometimes they are said to be the object of logic.
The term, rarely used in exactly the same sense by different authors, has long been associated with three equally ambiguous expressions: the law of identity (ID), the law of contradiction (or non-contradiction; NC), and the law of excluded middle (EM). The law of identity[edit] Law of Excluded Middle. In logic, the law of excluded middle (or the principle of excluded middle) is the third of the three classic laws of thought. It states that for any proposition, either that proposition is true, or its negation is true.
The law is also known as the law (or principle) of the excluded third, in Latin principium tertii exclusi. Yet another Latin designation for this law is tertium non datur: "no third (possibility) is given". The principle should not be confused with the principle of bivalence, which states that every proposition is either true or false, and has only a semantical formulation. Classic laws of thought[edit] The principle of excluded middle, along with its complement, the law of contradiction (the second of the three classic laws of thought), are correlates of the law of identity (the first of these laws). Analogous laws[edit] Some systems of logic have different but analogous laws.
Other systems reject the law entirely. Examples[edit] For example, if P is the proposition: and But if. Law of Noncontradiction. This article uses forms of logical notation. For a concise description of the symbols used in this notation, see List of logic symbols. In classical logic, the law of non-contradiction (LNC) (or the law of contradiction (PM) or the principle of non-contradiction (PNC), or the principle of contradiction) is the second of the three classic laws of thought. It states that contradictory statements cannot both be true in the same sense at the same time, e.g. the two propositions "A is B" and "A is not B" are mutually exclusive. The principle was stated as a theorem of propositional logic by Russell and Whitehead in Principia Mathematica as: The law of non-contradiction, along with its complement, the law of excluded middle (the third of the three classic laws of thought), are correlates of the law of identity (the first of the three laws).
Interpretations[edit] One difficulty in applying the law of non-contradiction is ambiguity in the propositions. Eastern philosophy[edit] Heraclitus[edit] Law of Identity. This article uses forms of logical notation. For a concise description of the symbols used in this notation, see List of logic symbols. In logical discourse, violations of the Law of Identity (LOI) result in the informal logical fallacy known as equivocation.[5] That is to say, we cannot use the same term in the same discourse while having it signify different senses or meanings – even though the different meanings are conventionally prescribed to that term. In everyday language, violations of the LOI introduce ambiguity into the discourse, making it difficult to form an interpretation at the desired level of specificity.
History[edit] Socrates: How about sounds and colours: in the first place you would admit that they both exist? Theaetetus: Yes. Aristotle takes recourse to the law of identity - though he does not identify it as such - in an attempt to negatively demonstrate the law of non-contradiction. Both Thomas Aquinas (Met. See also[edit] Allusions[edit] People[edit] References[edit] Rhetological Fallacies.