What is the deductive method?

We explain what the deductive method is and the ways in which it can be used. In addition, examples and what is the inductive method.

1. What is the deductive method?

We talk about the deductive method to refer to a specific way of thinking or reasoning, which draws logical and valid conclusions from a given set of premises or propositions . It is, in other words, a way of thinking that goes from the most general (such as laws and principles) to the most specific (concrete facts).

According to this way of thinking, the conclusions of a reasoning are given in advance in its own premises, so it only requires an analysis or breakdown of these to know the result. In order to do so, the premises must be considered true , since their validity will depend on whether the conclusions are true or not.

The deductive method can be used in two ways:

• Direct . In this case it is based on a single premise that is not contrasted with others around it.
• Hint . In this case it is based on a couple of premises: the first contains a universal statement and the second a particular one; the conclusion is obtained from the comparison of both .

In this way, it should be noted that the validity of the premises will determine that of the conclusions : it is possible to start from erroneous premises and deduce erroneous conclusions, without the reasoning reasoning logic being wrong.

On the other hand, this method gives rise to two other more complex methods, which are:

• Axiomatic-deductive method . A set of theorems (propositions) is extracted from a set of axioms (premises) given in advance, using a series of logical reasoning.
• Hypothetical method – deductive . From the observation of a phenomenon, an interpretive hypothesis is ventured and then subjected to comparison by logical reasoning of deductive type. This is the method that employs scientific knowledge.

2. Examples of the deductive method

Most syllogisms are a perfect example of the deductive method. Let’s see some:

• Premise 1. All dogs are deadly.

Premise 2. Pluto is a dog.

Conclusion. Pluto is mortal.

• Premise 1. No cow can fly.

Premise 2. Flying animals have wings.

Conclusion. Cows have no wings.

• Premise 1. Males have a penis.

Premise 2. Women are not men.

Conclusion. Women have no penis.

• Premise 1. Venezuelans are Caribbean.

Premise 2. Maria is Venezuelan.

Conclusion: Maria is Caribbean.

• Premise 1. The planets are round.

Premise 2. Earth is a planet.

Conclusion. The earth is round.

• Premise 1. The killer was a white male.

Premise 2. The maid is a Chinese woman.

Conclusion. The maid is not the killer.

3. What is the inductive method?

The inductive method is the opposite or opposite of the deductive, and therefore marches from the most particular to the most general. That is, the observation , recording and contrast of information is used to build general premises that can support or explain them.

That is, that the inductive method works from generalizations, supported by specific observations , that is, the other way around. For example:

Premise 1. My father died.

Premise 2. My father was a man.

Conclusion. The men die.