DEDUCTIVE METHOD: CHARACTERISTICS AND EXAMPLES - SCIENCE - 2024

The deductive method is a type of reasoning in which you start from generalities to reach specific conclusions. In the deductive reasoning process, one goes from facts or premises to arrive at logical conclusions; that is, it follows. If the facts / premises are true, the conclusion will also be true.

An example of the use of 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).

Example of deductive method

This methodology was used by the Greeks in ancient times; for this reason it is known as the first scientific method. However, this procedure has certain characteristics that prevent it from being considered entirely true.

Those who argue this in relation to the deductive method point out that it is possible to infer particular scenarios from universal principles, but that this does not imply that the former are true.

For this reason, the information collected through investigations that are based on the deductive method must later be corroborated through other mechanisms.

Characteristics of the deductive method

The deductive method is widely used in the formal sciences. Source: pixabay.com

Part of a universal principle

The approaches that are generated through the deductive method have their origin in a general statement.

This methodology is characterized because it goes from the most general to the most specific, since its main purpose is to assess the possibility of applying a universal principle in a particular setting.

It is not based on experimentation

This method is purely theoretical. For this reason, he does not base his studies on experiments or other actions that have the laboratory as a setting.

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 clearly rational and abstract.

It relies on logic

Logic and abstraction are elements that characterize the deductive method. In fact, logic is the way through which the argumentative structures are generated that allow the conceiving of specific scenarios based on general principles.

Is systematic

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

Represents the beginning of the search for knowledge

Thanks to the deductive method, it is possible to have information on possible specific scenarios that could be generated from notions of a universal nature.

For this reason, the observations generated in this area are in many cases the starting point for opening new lines of research and testing hypotheses.

What is this method for?

Thanks to the deductive method, it is possible to formulate theories and laws applicable to a specific context. By starting from a general principle, it is possible to predict these specific laws, as well as the nature of the influence they will have on certain scenarios.

Likewise, the deductive method allows to extrapolate the general premises. Therefore, the conclusions that are generated from this process are used to predict the behavior, or also the characteristics of a hypothetical scenario that is generated directly from the general foundation.

This implies that thanks to this method it is possible to generate hypotheses, which can then be developed in specific investigations. One of the reasons why this method is relevant is that it gives rise to new knowledge and new lines of study.

On the other hand, through the deductive method hypotheses can be tested. For this reason, this method is widely used when confirming or denying possible hypotheses in scientific research.

Steps

Determine the general principle to take into account

In the deductive method, the first action corresponds to choosing the universal premise from which we will start. This consideration must be completely true and valid, it must be an undeniable reality and as broad as possible.

It is essential to start from a general principle that is completely reliable, otherwise the entire deduction process that will be carried out in the following steps will be compromised, which implies that the result will probably not be valid.

To better exemplify this first step, let's use the following general principle example: “Diana is a woman”.

Apply the corresponding inferential laws

When making the transition between the general premise and the particular theorem, it is necessary to have a second premise, which must also be completely real and testable.

This second consideration takes into account an element related to the general principle and links it with a different one, but that has to do with the conclusion that is to be reached. An example of this can be the statement: "all women are human beings."

State the particular propositions

Once both statements have been determined, the next phase of the deductive method involves the presentation of the final conclusion that must be sustained in the veracity of the two previous premises, both of a general nature.

If we use the examples we have described to illustrate the previous phases, the particular proposition would be "Diana is a human being."

Confirm or deny the proposition

Once the specific premise that is based on general principles has been reached, it is necessary to verify the veracity of this statement. If it is not true, it must be denied and the premises must be raised in a different way.

Generate the corresponding laws

When it has already been verified that the definitive proposition has coherence, validity and veracity, it is possible to transcend this knowledge through the approach of laws or theories.

These laws have the function of defining the scenarios that have the characteristics represented in the conclusive premise. In this way it is possible to make it transcendental.

Types of deductive reasoning

- Law of detachment

A single statement is made and a hypothesis (P) is proposed. The conclusion (Q) is deduced from that argument and its hypothesis:

• P → Q (conditional statement)
• P (the hypothesis is proposed)
• Q (conclusion is deduced)

For this reason, it can be said that:

• If an angle satisfies 90 ° <A <180 °, then A is an obtuse angle.
• A = 120 °

A is an obtuse angle.

Examples of the law of detachment

• If my brother is 19 years old, and my sister is 21, and I am older than my brother and younger than my sister, then I am 20 years old.
• If we are five people in my family, and 3 of them are women, then two of them are men.
• If I have to buy 100 chocolate vanilla cakes, and I already have 60 chocolate cakes, then I am missing 40 vanilla.
• If the sum of all the angles in a triangle is equal to 180 °, and I have two angles of 30 each, then the third angle will be 120 °.

- Law of syllogism

In this law two conditional arguments are established and a conclusion is formed by combining the hypothesis of one argument with the conclusion of another. For example:

• If Pedro is sick, he doesn't go to school.
• If Pedro doesn't go to school, he will miss his homework.

So if Pedro is sick he will miss homework.

Examples of syllogisms

1. All women are beautiful.
2. Claudia is a woman.
3. Claudia is beautiful.

1. Some mammals swim.
2. I am afraid of animals that swim.
3. Some mammals scare me.

1. I like everything that has chocolate in it.
2. The cake has chocolate.
3. I like cake.

1. No human can fly.
2. Jaime is a human being.
3. Jaime cannot fly.

1. All dogs know how to bark.
2. Lucas is a dog.
3. Lucas knows how to bark.

1. Every Sunday I get sleepy.
2. Today it is Sunday.
3. Today I am sleepy.

1. Electric cars are expensive.
2. Renault launched an electric car on the market.
3. Renault's car is expensive.

1. All planets have a nucleus.
2. Saturn is a planet.
3. Saturn has a nucleus.

1. In all the cities of Peru it is hot.
2. Lima is a city in Peru.
3. It's hot in Lima.

- Counter-reciprocal law

This law states that, in a conditional, if the conclusion is false then the hypothesis must be false as well. An example of this law would be:

• If it is raining, then there are no clouds in the sky.
• There are no clouds in the sky, so it is raining.

Examples of the law of the counter-reciprocal

1. If she laughs, she is sad.
2. She is sad, then she is laughing

1. If it rains, the match is canceled
2. The match has been canceled, so it's not raining

1. I eat a lot when I'm stressed.
2. I'm not stressed, so I don't eat much.

Examples of deductive method

- José is a boy.

All children are human beings.

José is a human being.

- Plans are needed to make constructions.

A building is a construction.

To make a building you need plans.

- The water gets wet.

Carolina was in contact with water.

Carolina is wet.

- Salmon is a fish.

Fish live in the water.

Salmon live in water.

- If you touch the fire, you burn.

Pedro touched the fire.

Pedro was burned.

- People who wear glasses have difficulty seeing.

Cristina wears glasses.

Cristina has vision difficulties.

- If Antonio is ill, then he will be absent. If Antonio is absent, then his class work will be missed. Antonio is absent, therefore he lost his class work.

- If it is raining, there are clouds in the sky. There are no clouds in the sky, therefore it is not raining.

- Everyone who eats carrots is a quarterback. Juan eats carrots. Therefore, Juan is a quarterback. (Here you can see the weakness of the deductive method).

- Noble gases are stable. Neon is a noble gas, therefore neon is stable.

- This dog always barks when someone is at the door. The dog does not bark, so there is no one at the door.

- No one has lived more than 122 years. So, human beings die before the age of 122.

- All cows are mammals. Trina is a cow. So Trina is a mammal.

- All the women in my family have university degrees. My aunt Cintia is visiting us. So, Aunt Cintia has a college degree.

- Vegetables are healthy. The carrot is a vegetable. So, the carrot is healthy.

- Mexicans eat spicy. Nora is Mexican, so Nora eats spicy.

- Mammals suckle their young. The cat suckles his kittens, therefore the cat is a mammal.

References

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3. Vogel, M. "Deductive and inductive method within the scientific method" in Dashboard. Retrieved on November 9, 2019 from Dashboard: tabladecomando.com
4. Prieto, B. "The use of deductive and inductive methods to increase the efficiency of the digital evidence acquisition processing" at Pontificia Universidad Javeriana. Retrieved on November 9, 2019 from Pontificia Universidad Javeriana: magazines.javeriana.edu.co
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6. Bradford, A. “Deductive reasoning vs. inductive reasoning ”in Live Science. Retrieved on November 9, 2019 from Live Science: livescience.com
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