How it works
First, let’s understand what deductive reasoning is. It is usually described as taking the form of a syllogism — an argument in which a conclusion is inferred from two premises, one major and one minor. I find these terms confusing in explaining how deductive thinking works in writing, and so I will not use them again.

Instead, think of a deductive argument as needing to do three things:

• Make a statement about a situation that exists in the world.

• Make another statement about a related situation that exists in the world at the same time. The second statement relates to the first if it comments on either its subject or its predicate.

• State the implication of these two situations existing in the world at the same time.

Exhibit 18 shows several deductive arguments, each of which can be seen to do precisely these three things. And in each case the point at the top should roughly summarize the ideas grouped below, resting heavily on the final point. Thus, ‘Because Socrates is a man he is mortal,’ or ‘Since the unions behave as a monopoly, they should be controlled by the monopolies law,’ or ‘If you want to increase your volume, you must correct your present structure,’ and so forth.

如何运作

How it works

首先，让我们理解什么是演绎推理。通常，它被描述为一种三段论形式——一种基于两个前提（一个大前提和一个小前提）推导结论的论证。我认为这些术语对于解释演绎思维在写作中的运作方式是令人困惑的，因此我不会再使用它们。
First, let’s understand what deductive reasoning is. It is usually described as taking the form of a syllogism — an argument in which a conclusion is inferred from two premises, one major and one minor. I find these terms confusing in explaining how deductive thinking works in writing, and so I will not use them again.

相反，将演绎论证视为需要完成以下三件事：
Instead, think of a deductive argument as needing to do three things:

• 对世界中存在的某个情况作出陈述。
  Make a statement about a situation that exists in the world.

• 对同时存在的相关情况作出另一个陈述。如果该陈述评论的是前者的主语或谓语，则两者有关联。
  Make another statement about a related situation that exists in the world at the same time. The second statement relates to the first if it comments on either its subject or its predicate.

• 陈述这两个情况同时存在于世界中的含义。
  State the implication of these two situations existing in the world at the same time.

图表18展示了几个演绎论证的例子，每一个例子都可以被看作精确完成了上述三件事。每种情况下，顶部的观点应大致总结下方归组的思想，且强烈依赖于最终的结论。例如，“因为苏格拉底是人，他必定会死”；或者“由于工会的行为像垄断，它们应受垄断法管制”；或者“如果你想提升业务量，必须改正当前结构”等等。
Exhibit 18 shows several deductive arguments, each of which can be seen to do precisely these three things. And in each case the point at the top should roughly summarize the ideas grouped below, resting heavily on the final point. Thus, ‘Because Socrates is a man he is mortal,’ or ‘Since the unions behave as a monopoly, they should be controlled by the monopolies law,’ or ‘If you want to increase your volume, you must correct your present structure,’ and so forth.

Exhibit 18 Examples of deductive arguments

• Men are mortal → Socrates is a man → Therefore Socrates is mortal

• The purpose of the monopolies law is to stimulate production and distribution → The union monopoly over manpower stops production and distribution → Therefore the unions should be controlled by the monopolies law

• Any company that meets these three criteria will be worth buying → Company A meets all three criteria → Therefore Company A is worth buying

• Volume increases as a result of doing four things well → Your present structure makes it impossible for you to do any of these things well → Therefore you should correct your present structure

• The company has accomplished a great deal since its centralization of computer activities 5 years ago → However, it is neglecting some important opportunities to take advantage of its computer capability → Accordingly, it should refocus its approach to the present situation

  
  

图表18 演绎论证示例
Exhibit 18 Examples of deductive arguments

• 人皆会死 → 苏格拉底是人 → 因此苏格拉底会死
  Men are mortal → Socrates is a man → Therefore Socrates is mortal

• 垄断法的目的是促进生产和分配 → 工会垄断劳动力阻碍了生产和分配 → 因此工会应受垄断法管制
  The purpose of the monopolies law is to stimulate production and distribution → The union monopoly over manpower stops production and distribution → Therefore the unions should be controlled by the monopolies law

• 任何满足这三个标准的公司都有购买价值 → 公司A满足所有三个标准 → 因此公司A值得购买
  Any company that meets these three criteria will be worth buying → Company A meets all three criteria → Therefore Company A is worth buying

• 业务量的增长来自于良好完成四件事情 → 你的现有结构使得无法做好任何一件事情 → 因此你需要改正现有结构
  Volume increases as a result of doing four things well → Your present structure makes it impossible for you to do any of these things well → Therefore you should correct your present structure

• 自五年前集中化电脑活动以来，公司取得了很大成就 → 然而，它忽视了一些利用电脑能力的重要机会 → 因此，公司应重新调整其当前方法
  The company has accomplished a great deal since its centralization of computer activities 5 years ago → However, it is neglecting some important opportunities to take advantage of its computer capability → Accordingly, it should refocus its approach to the present situation

  
  

These are examples of deductive arguments in which each step of the reasoning has been included. But sometimes you will find yourself wanting to skip a step and chain two or more deductive arguments together, since to put in every step would take too long and sound pedantic. This chaining of arguments is perfectly permissible, provided that your reader is likely to grasp and agree with the missing steps. Exhibit 19 gives an example of a chained deductive argument that should probably go something like this:

We produce enough used newspaper to meet our own demand.
But we have done more than meet our own demand.
Therefore we have a shortage.

A shortage of used newspaper causes a shortage of newsprint.
We have a shortage of used newspaper.
Therefore we have a shortage of newsprint.

这些是包含每一步推理的演绎论证示例。但有时你可能希望跳过某些步骤，将两个或更多的演绎论证串联起来，因为写出每一步既冗长又显得教条化。这种串联论证是完全允许的，前提是你的读者可能掌握并同意省略的步骤。图表19展示了一个串联演绎论证的示例，其可能如下：
These are examples of deductive arguments in which each step of the reasoning has been included. But sometimes you will find yourself wanting to skip a step and chain two or more deductive arguments together, since to put in every step would take too long and sound pedantic. This chaining of arguments is perfectly permissible, provided that your reader is likely to grasp and agree with the missing steps. Exhibit 19 gives an example of a chained deductive argument that should probably go something like this:

我们生产的废旧报纸足以满足本地需求。
We produce enough used newspaper to meet our own demand.

但我们实际上生产的超过了需求。
But we have done more than meet our own demand.

因此我们存在短缺。
Therefore we have a shortage.

废旧报纸的短缺导致新闻纸的短缺。
A shortage of used newspaper causes a shortage of newsprint.

我们存在废旧报纸的短缺。
We have a shortage of used newspaper.

因此我们存在新闻纸的短缺。
Therefore we have a shortage of newsprint.

Exhibit 19 Examples of a chained deductive argument
Continued selling of used newspaper to Asian countries could aggravate the already short supply of newsprint in Southern California
→ The supply of used newspaper in Southern California is adequate to meet demand there now and in the future
→ However, Southern California sales to Asian countries have caused a severe shortage that will persist
→ This shortage of raw material will aggravate the already short supply of newsprint in Southern California

You can see how boring this argument would be to read if you put in every step, and in general that is my major complaint about the use of deductive arguments in writing. They are boring, primarily because they make a mystery story out of what should be a straightforward point.

图表19 串联演绎论证示例
Exhibit 19 Examples of a chained deductive argument

持续向亚洲国家出售废旧报纸可能会加剧南加州新闻纸供应的短缺。
Continued selling of used newspaper to Asian countries could aggravate the already short supply of newsprint in Southern California

→ 南加州废旧报纸的供应目前足以满足现在和未来的需求。
→ The supply of used newspaper in Southern California is adequate to meet demand there now and in the future

→ 然而，向亚洲国家销售废旧报纸已经造成了一个将持续存在的严重短缺。
→ However, Southern California sales to Asian countries have caused a severe shortage that will persist

→ 这一原材料短缺将加剧南加州新闻纸供应的短缺。
→ This shortage of raw material will aggravate the already short supply of newsprint in Southern California

你可以看出，如果写作中包含每一步，这种论证会非常无聊，这也是我对写作中使用演绎论证的主要抱怨。它们之所以无聊，主要是因为它们把本该直截了当的观点写成了一个“悬疑故事”。
You can see how boring this argument would be to read if you put in every step, and in general that is my major complaint about the use of deductive arguments in writing. They are boring, primarily because they make a mystery story out of what should be a straightforward point.