各位好, 小弟最近在研讀Mendelson的introduction to mathematical logic.
目前看到第一章第四節, 在談formal axiomatic thoery L.
其中有一段說 If A,B and C are any wfs(well-formed formulas) of L,
then the following are axioms of L:
(A1) ( A => (B => A) )
(A2) ( (A => (B => C)) => ((A => B) => (A => C)) )
(A3) ( ((┐B) => (┐A)) => (((┐B) => A) => B) )
實在不懂作者想表達的意思...這裡的axiom指的是公理嗎? 比方說實數系的公理那種?
還有就是well-formed formulas, 請問版上有人可以用數學的例子說明嗎?
thanks in advance.
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