pre2.txt

现在到了数学抽象中最关键的一步：让我们忘记这些符号所表示的对象。……（数学家）不应在这里停步，有许多操作可以应用与这些符号，而根本不必考虑它们到底代表着什么东西。
Hermann Weyl, The Mathematical Way of Thinking
(思维的数学方式)



We now come to the decisive step of mathematical abstraction: we forget about what the symbols stand for. ...[The mathematician] need not be idle; there are many operations which he may carry out with these symbols, without ever having to look at the things they stand for.
Hermann Weyl, The Mathematical Way of Thinking