Monday, March 04, 2013

Frege’s Puzzle

In his early writings on language, the great logician Gottlob Frege held that the meaning of a name is its reference. For example, the meaning of the name "Mont Blanc" is the mountain itself. But, in later writings, Frege argued that two names may have the same reference, yet differ in meaning. He reasoned that if the meaning of a name is just its reference, and two names have the same reference, then it should make no difference to the meaning of a sentence which name occurs in it Since "Hesperus" and "Phosphorus" are both names of the planet Venus, (l) "Hesperus is Phosphorus" and (2) "Hesperus is Hesperus" should have the same meaning. But Frege observed that they do differ in meaning, since (1) expresses a significant astronomical discovery, while (2) is a triviality. The explanation of why they differ in meaning is Frege's Puzzle. Frege's solution is that the meaning of a name is not only its reference, but also its sense.  The sense of a name is a condition that picks out the individual (if there is one) that satisfies that condition as the name's reference. Frege says that "Hesperus" and "Phosphorus" have different senses that pick out the same reference. This, he says, explains how (l) can be informative, while (2) is a triviality. Much 20th-century philosophy of language involves a discussion of Frege's notion of sense.

Remember: If "Hesperus" and "Phosphorus" are just different names for the same thing-the planet Venus-how can it be that "Hesperus is Phosphorus" and "Hesperus is Hesperus" differ in meaning?

Additionally: Many philosophers find the notion of sense obscure. The logician Saul Kripke argued that proper names do not have senses at all. In his view the reference of a proper name is not determined by a sense but by a chain of uses of the name that begins with an act of naming. For example, you may use the name "Thales" to refer to a certain preSocratic philosopher even though you don't know anything about him, as long as you acquired the name from someone who used it to refer to Thales.

30-SecondPhilosophies by Barry Loewer

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