Reasoning & Logic – the basics

How can logic help us sort out problems and make the right decisions? 

'Man is a Rational animal' – this is the classic definition (see this article here, where we put this into perspective – hint, we are not that rational).
Reasoning is the process of thinking about something logically and sensibly. It is the ability to think logically. When we say this, we are implying that we can think, use logic, and acquire objective knowledge.

Reason is a cognitive capacity, a form of awareness of the world. Cognition identifies things, and reason reacts to those facts, accesses them, and motivates us accordingly.

Reason and Logic reasoning

Through reason, we can generalize from perceptual observations and identify causal or non-causal regularities that are not evident to the naked eye. It gives us the ability to use language, make agreements, communicate, use abstract concepts, think about the future, plan, and imagine things that do not yet exist.

This post looks at aome basic terminology - we start with formal logic, deductive, inductive, and abductive reasoning.

Abductive reasoning is of particular interest to us, especially when dealing with complexity and visual thinking, which is looked at separately in more detail in a separate post (here)
For more on Deductive and Inductive reasoning, read this post on the 'scientific method.'

Logic is a study of good reasoning 

When we talk about logic, we are referring to formal (symbolic) language. Formal logic has to do with an argument's structure. Whether an idea is logically valid or one claim follows another.

Logic does not have to be done formally. We can use informal logic (critical thinking) when we need to reason or evaluate. We can use it whether the argument is strong or weak, regardless of what kind of conclusions we can draw.

However, there is a more significant distinction between formal and informal logic: deductive, inductive, and abductive reasoning.

Example of Symbolic Language

Example of Symbolic Language

A little terminology:

  • Reasoning involves making claims and statements, backing them up with reasons, and explaining the consequences. Propositions, which is part of the argument, are the issues we state.
  • Propositions can be true or false and are made as declarative statements. The fundamental point of reasoning is the 'argument', and by argument, we do not mean quarrels between people.
  • Argument = any number of premises as reasons for accepting the conclusion.
  • premise (assumed truth)is a step in an argument put forward toward establishing the conclusion.
  • proposition the meaning of a given sentence.
  • Arguments persuade, and explanation informs.
  • A sound argument satisfies three conditions – true premises, unambiguous premises, and valid logic


To arrive at a decision, we must go through a process of reasoning to choose among alternatives and make sense of information and data to draw conclusions, make predictions, or construct explanations. 

The primary forms of reasoning we use in the 'scientific method (see here) are deductive and inductive. But as you will see, we consider abductive reasoning the most appropriate when it comes to complex problems (see here). 

The three types of reasoning are summarised below. For a more detailed explanation of abductive reasoning, read this article

Deductive reasoning: conclusion guaranteed (top down approach)

This reasoning starts with a premise, general theory, statement, or hypothesis. It then works its way down to a conclusion based on evidence by examining various pieces of evidence.

It goes from premise to premise, ending in the conclusion that we can be certain of. Deductive arguments attempt to provide statements that guarantee the conclusion. It is concerned with validity and the truth. The argument is either sound (valid) or unsound (invalid). There is no middle ground. In an invalid argument, it could mean that one of the premises is incorrect if the conclusion is false.

This type of reasoning has been around since Aristotle.

For example:

Dr. Seuss hates cats (Hypothesis)
Then you provide examples of the cat in the hat that supports that hypothesis.
You can then deduce that Dr.Seuss does hate cats.

Credit ‘shmoop’.

Inductive reasoning: conclusion merely likely (bottom up approach)

This method originates from Francis Bacon. It starts with a small observation or question and works its way to a theory by examining the related issues - it is exploratory. The truth is reached by making repeated observations; then, we generalize the various observations into a probable conclusion.
We move from the concrete to the abstract – from the specifics to the general. The specifics are gathered into an organized pattern, producing the broader concept or idea known as an inductive leap.

An inductive argument only aims to provide statements that make the conclusion more probable. These arguments are either strong or weak. 

They can be affected by acquiring more premises (evidence) that will strengthen or weaken the argument. The aim is to offer an argument strong enough that, if the premises were to be true, then the conclusion is unlikely to be false.

No amount of inductive evidence will ever be 100% guarantee the conclusion. The simple reason for this is that some unobserved evidence might invalidate the hypothesis, or our conclusion might need revision in the light of new evidence.

The best inductive arguments make inductive leaps. We go beyond the information contained in the premises to some new claim about the world (the danger is if we go too far and imagine things that do not exist).


Taking the example of Dr. Seuss –
How does Dr. Seuss feel about cats?
He has a cat that is naughty, gets up to mischief, breaks things, children are scared of the cat, and the cat looks evil.
It does appear that Dr. Seuss does not like cats. (Hypothesis)

Abductive reasoning: taking your best shot

This method also originates with Francis Bacon, and starts with an incomplete group of observations, moving forward to the likeliest possible explanation for that group of observations. Abductive reasoning is used in daily decision-making and uses what information is at hand, which often is incomplete in either the evidence, explanation, or both.

This process can be creative, intuitive, and even revolutionary. Einstein's work is a good example – he used the 'thought experiment'.

Because we think this is an essential approach to reasoning when dealing with complexity. There's a separate, detailed post where we explore Abductive reasoning.

What is the difference between logic and reason?

Reason is dependent on personal opinion, whereas logic is the science that uses defined rules underpinning critical thinking. Logic pursues a tangible or visible proof of robust thought processes by reasoning.

Logic is an essential aspect of reason, but they are distinct. Logic is the method – a formal process done inside a system. In contrast, reason is done outside that system. It uses drawing diagrams, looking for examples, and observing changes when the rules have changed.

Only through reasoned thinking can we gain knowledge and understanding about the situations facing us. Reason yields clarity of thought, making us aware of the structure and relationship between facts, and drawing logical conclusions.

I know this post can be a little hard, but it is crucial to understand how there different aspects of reason work.