Deductive Argument

We tell you what a deductive argument is, its characteristics and examples. Also, the difference with an inductive argument.

What is a deductive argument?

An argument or deductive reasoning is a type of reasoning that goes from the general to the particular.. It is usually noted that this characterization is not exhaustive, since there are cases that exceed it, but it fits most of them. All deductive reasoning necessarily infers a conclusion from a series of premises.

The validity of deductive arguments is given by their form and their character of truth, which arises from a logical necessity. In a deductive argument, the truth of the premises implies the truth of the conclusion. It is logically impossible for the case in which the premises are true and the conclusion to be false.

Thus, the classic form of a deductive argument responds to the following example:

• Premise 1. All men are mortal.
  Premise 2. Socrates is a man.
  Conclusion. Socrates is mortal.

The first premise is a general statement. The second, a particular statement. If one starts from the statement that all men are mortal, and then takes a particular case in which it is stated that Socrates is a man, it must necessarily follow that Socrates is mortal. This is guaranteed by the rules of inference, which guarantee compliance with general laws.

Aristotle popularized the deductive argument through the syllogismand thanks to its form, the fact that it guarantees the validity of the argument and that the deductive argument is deduced naturally, the deductive argument or reasoning is one of the most used logical arguments.

Logical aspects of the deductive argument

A deductive argument is one in which valid, verifiable and communicable conclusions are obtained from one or more general premises.

Thus, if you want to obtain q from p then qwe can make the following deduction:

• p then q (general premise)
  p (particular premise)
  q (particular conclusion)

Examples of deductive arguments

• Premise 1: Fish swim.
  Premise 2: Dorado is a fish.
  Conclusion: El dorado swims.

• Premise 1: All men are mortal.
  Premise 2: Mauricio is a man.
  Conclusion: Mauricio is deadly.

• Premise 1: Whenever I pedal I use my legs.
  Premise 2: Pedaling.
  Conclusion: I use my legs.

• Premise 1: Everything that fire touches burns.
  Premise 2: I throw a plant into the fire.
  Conclusion: The plant burns.

inductive argument

The inductive argument is a reasoning that goes from the particular to the general. The fundamental difference between the deductive and inductive arguments is based on the logical path that each one proposes:

• The deductive arguments They start from general premises towards a particular conclusion. The conclusions are contained in the premises. It is a descending journey.
• Inductive arguments They start from particular premises to try to extrapolate a law or a general conclusion. The conclusions are obtained from a formulation of laws based on a generalization. It is an ascending journey.

There are other differences between both ways of arguing whose formality is less. Induction, for example, uses observation, recording and contrasting factual information to build general premises that serve as a basis for what is stated. In this reasoning we observe a leap of faith that can never occur in deductive reasoning: nothing can be stated that is not derived as a logical consequence of what has already been said.

References

• Gamut, LTF, & Durán, C. (2002). Introduction to logic. Buenos Aires, Argentina: Eudeba.
• Obiols, G. (1997). New Logic and Philosophy course. Kapelusz.
• Díez, JA (2002). Initiation to Logic. Ariel.