tractatus.04

3 different understandings on the function- "wittgenstein, Frege, Russel"

a function: X is white
frege: it is a referent that is input into that function, and the function outputs a true/false value.
russel: it is a referent that is input into that function, and the function outputs a propsition. and this proposition is "the meaning of that expression". だから関数は、命題内容、対象において働く。
wittgenstein: proposition is just an expression. 関数は論理形式解明のための道具。domain is not references but names. range is not a true/ false value, but a proposition, which is just an expression.