逻辑学 - 极简入门播客 - 第3集

大家好，欢迎来到这个简短的介绍。从古希腊到品牌塑造，全球化到荷马史诗，逻辑学到时尚潮流，我们将以简洁生动的方式带您领略一系列多元主题，满足您的好奇心探索。以下是今天的简短介绍。

Hi, and welcome to a very short introduction. From ancient Greece to branding, globalization to Homer, and logic to fashion, we'll showcase a concise and dynamic insight into a range of diverse topics for wherever your curiosity may lead you. So here is today's very short introduction.

向全球各地收听这个播客的朋友们问好。我是格雷厄姆·普里斯特，一位英裔澳大利亚哲学家。我最初是数学家出身，但学术生涯大部分时间都在哲学系工作。虽然最初最吸引我的是逻辑学——我们稍后会回到这个话题——但如今我对哲学的各个领域都充满兴趣。哲学是一门丰富深邃、引人入胜的学科。

Hello to everybody out there listening to this blog, wherever you are in the world. My name is Graham Priest, and I'm an Anglo Australian philosopher. I started life as a mathematician, but for most of my academic life, I've worked in philosophy departments. And although, originally, the thing that interested me most in philosophy was logic, we'll come back to that in a second, nowadays, I'm interested in most parts of philosophy. Philosophy is a rich and deep subject and a fascinating subject.

我曾在英国和澳大利亚多所大学工作任教，目前任职于美国。我是纽约市立大学研究生中心的教授，现在就是在这里与大家交流。多年前牛津大学出版社邀请我撰写《逻辑学简论》，我非常喜欢这个系列丛书，自己就读过其中好几本。

I've worked and taught in a number of universities in The UK and Australia, and my current position is in The United States. So I'm a professor at the Graduate Center of the City University of New York, which is where, essentially, I'm talking to you from. So quite a long time ago, OUP asked me to write the VSI on logic. I I really like the VSI series. I mean, I've read several of them.

除了当前这本书，我认为这套丛书在引导人们了解有趣领域方面做得非常出色。《逻辑学简论》于二月出版，2017年2月推出了第二版，已被翻译成多种语言——具体数量我已记不清，但上次统计时大约有十几种非英语版本。在接下来的播客中，我将简要谈谈逻辑学的魅力所在，特别是最吸引我的部分。

And the present volume aside, I think that they do a great job of introducing people to interesting areas. The Vadimon Logic came out in February. We went into a second edition in 02/2017, and I've lost count of the number of languages it's been translated into. But at the last count, it was sort like a dozen languages other than English. So what I'm gonna do in the rest of this podcast is talk a little bit about logic, what makes it interesting, and what interests me in particular.

让我们从

So let's start with a question of what logic is. And there's an easy and quick answer to that question, which is that logic is about reasoning. So reasoning is something that we all do. We reason from things we know to be true to figure out things we don't know. We reason from things we believe to show they might have consequences we don't accept and so we shouldn't believe them.

我们与自己辩论。我们与朋友及他人辩论。我们通过辩论试图说服他们某些事情。有时我们通过辩论试图指出他们的错误，这就是推理。而逻辑学正是研究推理的学科。

We reason with ourselves. We reason with friends and others. We reason to try to persuade them of things. We reason to try persuading their wrong sometimes, and this is reasoning. And logic is the subject which studies reasoning.

此刻你需要特别留意理解，因为你很可能误解我刚才的话。逻辑学并非研究人们实际如何推理——那属于认知心理学范畴。认知心理学研究告诉我们，人们很多时候推理能力非常糟糕。这不仅仅是由于困惑或醉酒等原因，而是人们在推理时会犯系统性错误。

Now you have to hear that in particular way because you might well misunderstand what I've just said. Logic is not about the way that people actually reason. That is a subject that belongs to cognitive psychology. And one thing we know from studies in cognitive psychology is that people reason very badly a lot of the time. And it's not just that they're confused or drunk or whatever, but people make systematic mistakes in reasoning.

认知心理学领域对此有大量文献记载。因此逻辑学关注的不是人们实际如何推理，而是应该如何推理。可以说，它研究的是推理的规范。逻辑学研究的是优质推理——什么样的推理是好的，以及为什么好。现在你们需要理解的第二个关键点是：

There's quite a large literature on this in cognitive psychology. So logic is not about how people actually reason, but how people should reason. If you like, it's about the norms of reasoning. So logic studies good reasoning, what reasoning is good, and why. Now the second thing you have to understand about what I mean by reasoning is this.

当你进行推理时，总是从某些起点出发，逻辑学家称之为前提，然后得出结论。逻辑学不关心前提本身——那是其他学科的问题。逻辑学关注的是从前提中真正能推导出什么。如果你告诉我一堆事实、信念或主张，作为逻辑学家，我会告诉你哪些结论能从中得出，哪些不能。

When you reason, you start from somewhere, logicians call these premises, and then you make conclusions. Logic is not concerned with the premises. That's someone else's problem. Logic is concerned with what really follows from premises. So if you tell me a bunch of facts or a bunch of beliefs or claims, then I, as a logician, will tell you what follows from these or what doesn't follow from these.

逻辑学家将这种推导关系称为有效性。因此逻辑学研究有效性——研究什么能从什么中得出以及为什么。正如我所说，逻辑学是对推理的研究，但它研究的是推理的规范而非心理过程；逻辑学家关心的是从任何给定前提中能推导出什么，而非前提本身。这听起来或许有趣，或许不然。

So logicians call what follows from what validity. So logicians study validity. It it studies what follows from what and why. So as I say, logic is a study of reasoning, but it's a study of the norms of reasoning, not the psychology of reasoning, and the reasoning that a logician is concerned with and not the premises, but what follows from whatever premises you have. That may or may not sound terribly interesting.

让我再多谈谈逻辑学，解释它为何既有趣又重要。首先，逻辑是一门非常古老的学科。西方逻辑学的起源可追溯至古希腊时期，与亚里士多德及斯多葛学派等哲学家相关，大约在公元前四五世纪。而在东方，逻辑学则源于被称为'正理派'的逻辑学家群体。

Let me say a little bit more about logic to explain why it's interesting and important. First of all, logic is a very ancient subject. The origins of logic in the West go back to ancient Greece with philosophers such as Aristotle and philosophers such as the stoics. So we're talking about the fourth, fifth century BC. In the East, it goes back to a group of logicians called the Neaia.

我们虽不确定其确切起源，但他们大约活跃于公元前后。因此逻辑学研究已有漫长历史，积淀深厚。这门学科已发展了两千年，但在二十世纪之交发生了重大转折——逻辑学家们首次将当时新兴的数学工具（如代数化方法等）应用于逻辑研究，由此引发了一场革命，使逻辑学达到了前所未有的深度与影响力。

We don't know their exact origin, but they're sometime around the time of the common era. So logic has been studied for a very long time, and it has a rich and deep history. It's been progressing now for, okay, so two thousand years, but something very significant happened around the turn of the twentieth century when logicians really started to take the tools of mathematics that were then being delivered, such as algebraicization and so on, and apply them to logic for the first time. And this caused a revolution in logic. It made logic subject of power and depth that had not been achieved before with significant consequences.

其中一个重要成果就是计算理论的奠基，这远在实际计算机发明之前。现代逻辑学在许多实用领域都产生了深远影响。所以说，逻辑学既是古老又是现代的学科，其发展历程本身也极富魅力。若非专业学者，为何要关注逻辑？因为我们都在进行推理。

So one of these was laying the theory of computation, a long time before practical computers were developed. So modern logic has important consequences in very practical areas. So logic is a subject which is both very ancient and very modern, and it has a fascinating history, which is another matter. Why should one be interested in logic if one's not a logician? We all reason.

每个人都会推理，且不必专门学习逻辑也能有效推理。许多人天生擅长推理，多数推理过程遵循显而易见的原则——比如'苏格拉底是人，凡人皆有一死，故苏格拉底会死'，这种推论无人质疑。

Everybody reasons, and you don't have to study logic to be a good reasoner. Many people reason well, naturally, and lots of reasoning uses principles with a pretty obvious, you know. Socrates is human. All humans are mortal, so Socrates is mortal. No one's gonna argue about that.

但当涉及数学、哲学、法律等领域时，推理常变得异常复杂。推理链条可能极其冗长，涉及众多前提并以复杂方式联结。正是在这种艰难时刻，逻辑学展现出其实用价值——不是作为理论空谈，而是作为实践工具。这是人们重视逻辑的第一个原因。

But reasoning often gets very complicated and difficult, particularly in areas such as mathematics and philosophy and law. Chains of reasoning can be very complex. Many, many different premises may be involved, and many ways they can be chained together in complex ways. So when the going gets tough in reasoning, that's when I think logic becomes really useful, not as a theoretical enterprise in its own right, but, as a as a practical enterprise. This is one reason why people are interested in logic.

第二个原因在于逻辑学与哲学有深刻渊源。逻辑学至今仍是哲学系的核心课程（当然也见于数学系和计算机系），这并非偶然。不仅因为哲学家需要推理（他们确实需要），更因为逻辑学研究'结论如何从前提得出'及'为何如此'——这个'为何'会引向关于实在本质的形而上学追问。

Another reason why people are interested in logic is that logic actually has roots which sink deep into philosophy. So it's no accident that logic is studied in philosophy departments. Nowadays, it's studied in mathematics departments and computer science departments as well, but it's always had an important home in logic. And this is not just because philosophers reason. They do, of course, on a good day.

逻辑学的根基深植于哲学问题，而这些哲学问题反过来塑造了逻辑理论的发展。稍后我会举例说明，但首先要强调：逻辑学之所以重要，不仅关乎推理技艺，更因其与根本性哲学问题紧密相连。

Rather, logic is concerned with what follows from what and why. And the why question is important because once you start to look at the why question, you soon sink deep into questions of the nature of reality, metaphysics, if you wanna call it that. The roots of logic sink deep into philosophical questions, and those philosophical questions in turn affect the logical theories that eventuate. So, I'll give you some examples of that in a moment, but let me just flag this as another reason why logic is an important subject. Because it's not simply about reasoning, its roots sink deep into deep philosophical questions.

最后谈谈我研究逻辑的契机。作为数学背景出身，最初吸引我的是逻辑学中的技术性问题——其中存在大量有趣的数学课题。但随着深入研究，我逐渐体会到逻辑学与哲学其他领域及前述形而上学问题的深刻关联。事实上，当受邀撰写《逻辑学简论》时，我最初是拒绝的。

The last thing I'll talk about is why I got interested in logic. Since my background is in mathematics, I guess the first thing that interested me about logic was some of the technical stuff. So there are many interesting technical questions, mathematical questions in logic, and with my mathematical background, I was naturally interested in those. But once I've studied more and more logic, I came to appreciate the connections between logic and the rest of philosophy and these kind of deep metaphysical questions that I talked about. Indeed, when I wrote the VSI in logic, when I was asked to do this, I said, no.

我认为用五万字介绍逻辑学根本不可能。但编辑建议：'何不选取若干哲学问题，阐释逻辑学与之的关联，并顺带讲解逻辑技术？'这个建议非常高明——最终我也采用了这种写作方式。

This is impossible. You can't introduce logic in 50,000 words. And the editor of time said to me, well, look. Why don't you think of it like this? Take some philosophical problems and explain the relevance of logic to these, and you can explain some techniques of logic along the way.

那么逻辑学究竟关联哪些根本问题？例子不胜枚举，比如关于上帝存在的探讨...

And that was she was right. It was a very good suggestion. So that that's the way I wrote the VSI. Now, what sorts of problems does logic sink its roots into? Well, there there are so many, but there are questions about God, for example.

这些问题涉及时间与变化、真理与存在、语言与悖论，都是深奥的形而上学或哲学议题。在这本《非常短介绍》中，我探讨了逻辑与其中一些问题的关联。就我个人而言，逻辑学除了能证明若干定理外，最令我着迷的正是它与深刻哲学问题之间的深层联系。好的。

There are questions about time and change, truth and existence, language and paradox. So these are all deep metaphysical or philosophical issues. And one thing I do in the VSI is explore the connections between logic and some of these issues. And as I say, what I love about logic personally, apart from the fact that it can prove a few theorems, is the fact that it has these deep connections with profound philosophical questions. Okay.

现在不是深入探讨这些问题的适当时机和场合。若想了解具体内容及其与逻辑学的关系，恐怕您得购买这本书了。

This is not the time or the place to go into those questions further. If you want to see what they are and their relationship to logic, then I'm afraid you're gonna have to buy the book.