8 junio, 2024

Deductive method: what it is, steps, characteristics, simple examples

What is the scientific method?

He Deductive method it is a form of reasoning that derives from the scientific method and whose purpose is to obtain logical conclusions from a group of premises; that is, it is deduced. If the facts or premises are true, the conclusion will also be true.

An example of using the deductive method is: 1-All men are living beings (first premise). 2-Albert Einstein is a man (second premise). 3-Therefore, Albert Einstein is a living being (conclusion).

As can be seen in the example, first one starts from a general notion or rule (men are living beings) to reach a concrete or particular conclusion (Einstein is a living being). It must be taken into account that the conclusions of the deductive method are not necessarily true; sometimes they can be wrong.

This type of reasoning is guided by logic and forces the researcher or student to use both observation and rational thought.

Types of deductive method

According to the strategy used, the deductive method can be:


It is direct when the researcher starts from a single premise to reach a conclusion. That is, it does not require another premise that serves as a bridge or comparison.


The indirect method is much more used than the direct one. It is considered indirect because the researcher uses two premises to reach a conclusion.

Usually, the first premise is based on a universal law, while the second focuses on a particular fact. The conclusion is obtained after both premises are reasoned and compared. For example:

Premise 1: All mice have big ears and a tail.
Premise 2: Mickey has big ears and a tail.
Conclusion: Mickey is a mouse.

Steps to apply the deductive method

To use this method, the following steps must be followed:

1. Define the first premise

To establish the first premise you must start with observation. That is, first a situation or universal fact is observed that allows the construction of the premise that will guide the rest of the deductive reasoning.

For example: Pedro observed that plants have roots; therefore, his first premise will be «all plants have roots.»

2. Define the second premise

When observing a fact and designating the first premise, another premise must be built that will serve as a comparison with the first and that will allow a logical conclusion to be found.

According to the previous example, the process would be as follows: After observing that all the plants have leaves and roots, Pedro realized that his cactus has roots. Therefore, Pedro established the following premises:

Premise 1: All plants have roots.
Premise 2: My cactus has roots.
From the comparison of both premises, Pedro will be able to reach a logical conclusion.

3. Establish the conclusion

After elaborating the two premises, we proceed to establish a pertinent conclusion. The conclusion is always logical, but it is not necessarily correct in all cases.

Finally, Pedro’s deductive method would be as follows:

Premise 1: All plants have roots.
Premise 2: My cactus has roots.
Conclusion: my cactus is a plant.

As can be seen, Pedro started from a general law (all plants) to analyze a particular fact (his cactus). Although this method is widely used by researchers and scientists, it is also used by all people in their daily lives, even unconsciously.

Characteristics of the deductive method

Starting from the general to arrive at a particular fact

The deductive method begins its reasoning from a universal notion or law, that is, it applies to all things or to most of them. It should not be confused with the inductive method, which works in the opposite way, starting from the particular to reach the general.

This is observed in the following deductive reasoning:

All living things eventually die.
The human being is a living being.
The human being eventually dies.

It is used in different aspects of life

The deductive method is used by researchers and scientists from all areas, especially those disciplines that require observation. However, deductive reasoning is not exclusive to the academic world, since it is also used by people in daily life many times automatically.

It works from logic

Logic is a science that analyzes the structure of human thought and that seeks to establish principles or laws that allow obtaining truths. For this reason, it is said that the deductive method uses logic to carry out its reasoning, since its purpose is to obtain valid conclusions that can become true.

Not based on experimentation

This method is theoretical. For this reason, he does not base his studies on experiments or other actions that take place in the laboratory.

It is a methodology with a much more argumentative and predictive approach, with special application in the so-called formal sciences, those disciplines whose basic knowledge is rational and abstract.

it’s systematic

The deductive method is carried out through a series of defined and well-structured processes. This order in the application is essential to obtain useful results.

Examples of using the deductive method

Here are some examples of deductive method:

dolphins don’t fly

Premise 1: No dolphin can fly.
Premise 2: Animals that can fly have wings.
Conclusion: Dolphins don’t fly because they don’t have wings.

The cat suckles

Premise 1: All mammals breastfeed.
Premise 2: My cat is a mammal.
Conclusion: my cat breastfeeds.

Venus is spherical

Premise 1: All planets are spherical.
Premise 2: Venus is a planet.
Conclusion: Venus is spherical.

beetles are invertebrates

Premise 1: Insects are invertebrate animals.
Premise 2: Beetles are insects.
Conclusion: beetles are invertebrates.

Tuna breathe underwater

Premise 1: Fish can breathe underwater.
Premise 2: tuna is a fish.
Conclusion: tuna can breathe underwater.

Andrea is elderly

Premise 1: People who use a cane belong to the elderly.
Premise 2: Mrs. Andrea uses a cane.
Conclusion: Mrs. Andrea is elderly.

The cactus needs water and light

Premise 1: All plants need light and water to survive.
Premise 2: my cactus is a plant.
Conclusion: my cactus needs water and light to survive.

the lion can roar

Premise 1: All lions can roar.
Premise 2: There is a lion in the animal shelter.
Conclusion: the lion in the animal shelter can roar.

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