Mathematicians of the constructivist school (Brouwer, Stolzenberg, Bishop) object to the unqualified use of this rule when statements about existence are involved. They contend that in order to prove that a mathematical object exists, you must first supply an effective method for constructing it. According to constructivist, it is not sufficient to assume that the object dose not exist (RAA hypothesis) and then derive a contradiction.
The law of the excluded middle is characteristic of two-valued logic:either a statement holds or it dose not; there is no middle ground. This has sometimes been described as "God's logic" even if we mortals can't tell whether a statement is valid, God knows. In recent years, research has begun on many-valued logic (Lukasiewicz, Post, Tarski), and this work is beginning to have applications (e.g., theory of fuzzy sets").
Mathematicians of the constructivist school (Brouwer, Stolzenberg, Bishop) object to the unqualified use of this rule when statements about existence are involved. They contend that in order to prove that a mathematical object exists, you must first supply an effective method for constructing it. According to constructivist, it is not sufficient to assume that the object dose not exist (RAA hypothesis) and then derive a contradiction.The law of the excluded middle is characteristic of two-valued logic:either a statement holds or it dose not; there is no middle ground. This has sometimes been described as "God's logic" even if we mortals can't tell whether a statement is valid, God knows. In recent years, research has begun on many-valued logic (Lukasiewicz, Post, Tarski), and this work is beginning to have applications (e.g., theory of fuzzy sets").
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