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A condition can be both necessary and sufficient. For example, at present, "today is the Fourth of July" is a necessary and sufficient condition for "today is Independence Day in the United States". Similarly, a necessary and sufficient condition for invertibility of a matrix M is that M has a nonzero determinant.
It is a necessary condition that an object has four sides if it is true that it is a square; conversely, the object being a square is a sufficient condition for it to be true that an object has four sides. [4] Four distinct combinations of necessity and sufficiency are possible for a relationship of two conditions. A first condition may be ...
The absence these conditions guarantees the outcome cannot occur, and no other condition can overcome the lack of this condition. Further, necessary conditions are not always sufficient. For example, AIDS necessitates HIV, but HIV does not always cause AIDS. In such instances, the condition demonstrates its necessity but lacks sufficiency.
Causes may sometimes be distinguished into two types: necessary and sufficient. [19] A third type of causation, which requires neither necessity nor sufficiency, but which contributes to the effect, is called a "contributory cause". Necessary causes If x is a necessary cause of y, then the presence of y necessarily implies the prior occurrence ...
In philosophical terminology, "cause" can refer to necessary, sufficient, or contributing causes. In examining correlation, "cause" is most often used to mean "one contributing cause" (but not necessarily the only contributing cause). Dinosaur illiteracy and extinction may be correlated, but that would not mean the variables had a causal ...
A component cause is a factor that, along with other component causes, forms a sufficient cause for a disease. A sufficient cause is a complete combination of component causes necessary for the disease to manifest. Diseases result from a chain of causally related events, starting from an initial event to the clinical appearance of the disease.
Therefore A is the cause, or the effect, or a part of the cause of w. As an example of the method of difference, consider two similar countries. Country A has a centre-right government, a unitary system and was a former colony. Country B has a centre-right government, a unitary system but was never a colony.
Sufficient and necessary causes [ edit ] Causality, within sociology, has been the subject of epistemological debates, particularly concerning the external validity of research findings; one factor driving the tenuous nature of causation within social research is the wide variety of potential "causes" that can be attributed to a particular ...