| ＂我說謊＂的挑戰
語言，可以說是屬於人類＂熟知而非真知＂的事物之一。
語言存在的問題之一，就是悖論的存在，如＂我說慌＂，這句話使人無法辨認真假。比較經典的還有羅素發現的＂最大集悖論＂問題。一個最大的集，應該包括其他一切集。問題是，它是否應該包括自己？如果不包括，它就不是最大集。如果包括，就違反了＂包括其他一切集＂的規定。
通俗地說，羅素悖論也叫＂理髮師悖論＂。一個理髮師作廣告說，＂我只給全城不自己刮鬍子的人刮鬍子＂。理髮師，很明顯，無法確定是否應該給自己刮鬍子。因為，按照廣告，如果自己不屬於＂自己刮鬍子＂的人，那麼，自己就必須自己給自己刮鬍子。而如果自己屬於＂給自己刮鬍子的人＂，自己就不應該給自己刮鬍子。 據說，當福雷格接到羅素的明信片時，立刻叫停了馬上就要開印的幾卷本的數學基礎論著作，它一生努力的工作付之東流。
所以，究竟為什麼語言會出現悖論？悖論僅僅是人類語言的錯誤嗎？還是也存在於自然界？我們應該怎樣來理解悖論？
等等這些問題，一個世紀以來，人類還在繼續尋找答案......
Reference:
"Russell's Paradox
Russell's paradox is the most famous of the logical or set-theoretical paradoxes. The paradox arises within naive set theory by considering the set of all sets that are not members of themselves. Such a set appears to be a member of itself if and only if it is not a member of itself, hence the paradox.
Some sets, such as the set of all teacups, are not members of themselves. Other sets, such as the set of all non-teacups, are members of themselves. Call the set of all sets that are not members of themselves “R.” If R is a member of itself, then by definition it must not be a member of itself. Similarly, if R is not a member of itself, then by definition it must be a member of itself. Discovered by Bertrand Russell in 1901, the paradox has prompted much work in logic, set theory and the philosophy and foundations of mathematics."
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