How to Reason?

The universal answer to this question is- Carefully.

But how does one go about reasoning carefully? First, one must learn the primary tool of reasoning: Logic. Here we offer a glimpse of formal logic but move on to an alternative approach to formal logic. We argue that in real life context, an exhaustive knowledge of formal logic is rarely useful. Formal logic was, and still is, essential for studying computer science, mathematical proofs and epistemology. This section will explain some fundamentals of formal logic, but only to the extent which is necessary for one to understand the nature of logical structures.

On reasoning carefully, the next section on dialectic, we will take you through some helpful tools of thinking and rethinking.

Why is logic useful?

Ordered Thinking

If you are wondering what you can do with logic, the answer is that logic can do something with you. But what is Logic? Logic builds the mental habit of thinking in an orderly way, it can be described as reasoning conducted or assessed according to strict principles of validity. Even if you forget the details of a lesson in logic, you will become more habitually aware of the structure of logic, just as you are aware of a second language after forgetting the details of its grammar or some of its vocabulary. Logic studies the structures of thought. Just as objects in the material universe, thoughts have structures too. Thought is not a blank screen, receiving its form only from the world that appears on it.
No lesson is more practical than one in logic, for no matter what you are thinking about, you are thinking, and logic orders and clarifies your thinking, no matter the content of your thought. The principles of thinking logically can be applied to all thinking and to every field.

Power of Proof and Persuasion

Any power can be used or abused. The power of logic is rightly used to find truth and rectify errors; it is wrongly used to win arguments and defeat our opponents. 


Logic is a tool that is used across disciplines. You are always going to be reading books or listening to lectures, podcasts, speeches, and logic will help you think more clearly and effectively when you read, listen and learn. It is not a far-stretch to speculate that one of the biggest reasons for the steep decline in our reading ability is the decline in teaching of traditional logic. 


Clear writing and clear thinking come in a package. The presence or absence of either one brings the presence or absence of the other. Muddled writing fosters muddled thinking, and muddled thinking fosters muddled writing. Clear thinking fosters clear writing, and clear writing fosters clear thinking. 

Testing Authority

We need authority as well as logic. 

We need authority because no individual can discover everything on their own. We all have to rely on expert consensus when it comes to physical sciences and other scientific disciplines. However, we need logic to test our authority. There is another reason we need logic when it comes to authority: we need to have good reasons for believing authorities, for in the end, it is the individual you who decides which authority to trust.

Reducing Uncertainty 

Formal logic guarantees absolute certainty. However, formal logic is not the focus of this chapter. We focus on informal logic, which is of more use when it comes to our daily lives. But informal logic cannot guarantee absolute certainty. Unlike formal logic, informal logic aims to reduce uncertainty and guarantees higher degrees of accuracy. 


Philosophy means ‘the love of wisdom’. Etymologically speaking, the term comes from the Greek words philos, meaning friend or lover, and sophia, meaning wisdom. Although logic alone cannot make you wise, it can help. For logic is one of philosophy’s main instruments. Logic is to philosophy what telescopes are to astronomy or math is to physics. A quintessential stepping stone which should not be avoided.

Why care about Reason?

As you can see from the example from the previous page, the case was a significant example where society as a whole failed to reason properly. It indicated that we are not quite as clever as we think we are, and that seeing through faulty claims is often complex. Our capacity to reason can be hijacked by context, powerful rhetoric and biases. Disarming manipulators is a noble goal by itself, but you are not going to find reasoning useful only when the higher stakes are higher. Reasoning ability can help you in your day to day lives, improving your ability to make objectively better decisions, getting better at reading, or having constructive conflicts, to name a few. After reading this section, you will find you are using tools of reasoning in cases you may not be aware of right now. The primary tool of day to day reasoning is informal logic, which is exhaustively described in this section.

“We often hear questions such as: “Who decides reason, why should we trust reason?” These questions are, in reality, but claims in disguise. The confusion about reason stems from our misunderstanding on the nature of rational thinking. The division between reason and emotion is a false dichotomy. As the neuroscientist Antonio Damasio aptly put it: “We are not necessarily thinking machines, we are feeling machines that think”. Or to reverse Descartes: we are, therefore, we think.

The McCarthy Trials

During the cold war, the US and the Soviet Union were at ideological conflict. Joseph McCarthy, a prominent US senator, set out on a mission to identify the dangerous ‘communists’ allegedly trying to infiltrate the US government. A commission was set up to prosecute these so-called communist spies within the state. Through an arbitrary selection process, the accused was presented in a senate committee hearing. The only way the defendant could be acquitted is by proving that they were not a ‘communist’. Let’s take a look at the ‘McCarthy Method’ through the lens of Reason:

A hyperbolic example:
Proof that UFOs exist

  • You cannot prove that UFOs don’t exist

Therefore, UFOs must exist.

No person in good sense would agree with the conclusion. Because, the logical structure is blatantly lacking.

The McCarthy Argument:

  • You cannot prove that you are not a communist.

Therefore, you must be a communist.

The logical structure they both follow contains the form:

  • You cannot prove X is not true
  • Therefore, X must be true