Is metaphysics just a bunch of nonsense? Is it okay to believe something you could never prove? Could logic be a solution to the world’s problems? This week on中国伊朗亚洲杯比赛直播, we’re thinking about theVienna Circle20世纪20年代的一群奥地利哲学家对这些问题进行了辩论，试图开创一个有科学基础的思考的新时代。

While the philosophers of the Vienna Circle (including Rudolf Carnap, Otto Neurath, and the circle’s central figure, Moritz Schlick) had plenty of disagreements, they agreed on some general principles: science and logic are the best tools for understanding the world; a statement is only meaningful if you can test it using experiments and observations; and metaphysics is meaningless.

Many religious debates are meaningless by the standards of the Vienna Circle. Sure, itseemslike everyone understands what you’re saying when you talk about God, but the philosophers of the Vienna Circle would disagree. God’s existence makes no difference to what we can see and hear and touch. The fact that we can’tdisproveHer existence, any more than we can disprove the existence of the Loch Ness Monster, is no help at all.

但究竟要怎样才能用观察来检验一个命题呢?有些陈述即使是正确的你也无法证明，但如果是错误的你仍然可以反驳。(例如，观察一只黑天鹅足以反驳所有天鹅都是白色的理论，但观察白天鹅再多也不足以证明这一点……如果你在某个地方错过了一只黑天鹅怎么办?)一个理论是否被一个被认为极不可能，但并非不可能的观察结果所推翻?如果你的实验室实验与公认的物理定律相矛盾，难道你不应该认为你的设备坏了吗?

Mathematics also creates trouble for the idea that all meaningful statements can be tested experimentally. We know that 2+2=4, and it seems like no experiment could prove otherwise. One answer to the puzzle, proposed by the Vienna Circle’s founder Moritz Schlick, is that math is true by definition: it follows from certain axioms by rules of deductive proof. But another member of the group, Kurt Gödel, showed thatthere are some seemingly true sentences about mathematics that cannot be proved using the usual axioms, and that adding extra axioms won’t help.

如果数学的定义是正确的，那么我们到底在讨论谁的定义呢?我可以重新定义2+2 = 5吗?鲁道夫·卡尔纳普(Rudolf Carnap)等哲学家认为，真理是相对于一组定义而言的，我们应该基于实践的基础来选择我们的定义。我们通常对数字的定义是2+2总是等于4，我们应该坚持这些定义，因为它们在从会计到工程的广泛领域都很有用。

The philosophers of the Vienna Circle were constantly debating and refining the finer points of their ideas about meaning, observation, logic, and science. While the details of their views are contentious, I think they had some obvious insights that have changed philosophy for the better. They pointed to an important difference between theories in disciplines like chemistry, which can be tested by experiments, and horoscopes in the newspaper, which are vague enough to fit with nearly any observation—even if it’s a struggle to spell out exactly what that difference is. And they encouraged philosophers to give precise definitions for their terms—even if we sometimes disagree about when a definition is precise enough.

We’ll be talking more about the Vienna Circle this week with David Edmonds, author ofThe Murder of Professor Schlick: The Rise and Fall of the Vienna Circleand host of thePhilosophy Bitespodcast. I can’t wait to discuss the lives and ideas of this under-appreciated group of philosophers.