立兄在博文评论中指出我使用“理论（theory）”的不严谨之处。仔细想了想，还真是。理论是结合了若干观察结果和假说，经过充分检验而广为接受的解释（A theory is a well tested, widely accepted explanation that combines several observations and hypothesis）。我在《错误的理论也比没有理论强》中所谓的“理论”使用不严格，应该是hypothesis才对。当然，理论也可能最后证明不一定正确。

一般人使用“理论（theory）”一词，含义通常与严格的科学定义是不同的。日常谈话中所谓的理论，其意思相当于一种直觉或猜测，并不是科学上认为的证据支持的解释（理论）。正如：The word "theory" is often heard in science, but the way scientists use it is different from the way it's used in everyday conversation. When you say a theory, you probably mean a hunch or a guess. In science, by contrast, a theory is an explanation for the way reality works that has considerable supporting evidence. For a theory to be accepted, it must first pass the test of experiment and observation not just once but many times.（https://www.theclassroom.com/must-happen-scientific-theories-accepted-valid-7454.html）

达到严格的“理论（theory）”，第一步应当是猜想或假说（hypothesis），猜想或假说经过实验验证后，才能上升为理论。即：Assuming a hypothesis meets the necessary criteria, scientists will test it by experiment. If numerous experiments and observations are consistent with the hypothesis, the hypothesis may eventually come to be called a theory, indicating it is consistent with all the available evidence and is now widely accepted. What distinguishes a theory from a hypothesis, in other words, is that a theory has been repeatedly tested using different kinds of experiments and been found valid in every case thus far.（https://www.theclassroom.com/must-happen-scientific-theories-accepted-valid-7454.html）。

但当有新的实验或观察结果不符合理论时，旧的理论就会被抛弃。即：Truth in science is never final but is always subject to modification and revision. Sometimes a theory may come to be widely accepted, but then a new experiment or observation may provide evidence inconsistent with the theory and force scientists to discard it in favor of a new explanation. It just takes one experimental result inconsistent with a theory to show the theory is wrong, but a thousand experiments can't prove the theory is right.（https://www.theclassroom.com/must-happen-scientific-theories-accepted-valid-7454.html）

另见：What makes a theory accepted or not accepted?（https://wise-answer.com/what-makes-a-theory-accepted-or-not-accepted/）

另外一篇文章是关于理论（theory）和事实（fact）的区分，我觉得写得也相当不错。见：

When does a theory become a fact and who decides?

其中

Wolf Kirchmeir的意见如下：
理论永远不会成为事实。它是对一个或多个事实的解释。（A theory never becomes a fact. It is an explanation of one or more facts.）

Nick Canning的意见如下：

一个理论的“真理性”取决于它在联系大量事实和预测尚未观察到的新事实方面的有用性。发现不符合理论的事实将导致寻找新的理论。（The “truth” of a theory is determined by its usefulness in linking the largest number of facts and predicting new ones that haven’t been observed yet. Discovery of facts that don’t fit the theory will lead to the search for a new theory.）

Matt Chamings的意见如下：

理论并不是关于什么可能是真实的推测。它是一组命题，旨在解释一种特殊现象或一组事实。理论可以根据证据的需要，来测试和证明是否准确的或需要修改。即使一个理论被接受为事实，它仍然是一个理论。（A theory isn’t speculation about what might be true. It is a set of propositions that seek to explain a particular phenomenon or set of facts. A theory can be tested and shown to be accurate or modified as the evidence requires. Even when a theory is accepted as fact, it remains a theory.）

Alan Harding的意见如下：

虽然像艾萨克·牛顿的万有引力理论这样的科学理论做出了无数次的预测，但它只能通过有限的观测来验证，因此它永远不会被视为无可辩驳的正确。在哲学上，这是归纳法的问题。科学建立在相当脆弱的认识论基础上，这一事实使它受到反科学运动的攻击，例如，神创论者声称达尔文进化论“只是一种理论”。在某种程度上，所有的科学都“只是一种理论”，但它的强大之处在于，不符合现实世界观测的理论最终会被抛弃。牛顿的万有引力理论就是这样，现在被视为广义相对论的一个特例。因此，实际上，在科学领域，我们没有事实或证据，我们所拥有的只是当时可用的、最广泛接受的理论。（While a scientific theory such as Isaac Newton’s theory of gravitation makes an infinite number of predictions, it can only be verified by a finite number of observations, so it can never be seen as irrefutably correct. In philosophy, this is the problem of induction. The fact that science rests on rather fragile epistemological foundations opens it to attack from anti-science movements, for example when creationists claim that Darwinian evolution is “only a theory”. All science is, to some extent, “only a theory”, but its great strength is that theories that don’t fit real world observations are eventually discarded. This has happened with Newton’s theory of gravitation, now seen to be a special case of general relativity. So in reality, in science we do not have facts or proof, all we have is the best-available, most widely accepted theory at the time.）