Deductive method is an information analysis process that uses the logical reasoning and the deduction to reach a conclusion about a particular subject.
In this process, deductive reasonings present conclusions that must necessarily be true, if all the premises are also true and he respects a logical structure of thought.
This method is usually used to test existing hypotheses, called axioms, in order to prove theories, called theorems. Therefore, it is also called a method. hypothetical-deductive.
It is then directly related to the principle of deduction, which means the act of concluding or minutely enumerating facts and arguments to reach a conclusion.
Learn more about Logical reasoning.
In the deductive method, the researcher starts from principles recognized as true, called major premise, and establishes relationships with a second proposition, called minor premise. In this way, based on logical reasoning, one arrives at the truth of what is proposed, the conclusion.
Example: Every mammal has a heart. (Major premise - axiom)
Now all dogs are mammals. (Minor premise)
Therefore, all dogs have a heart. (Conclusion - theorem)
The deductive method has its origins attributed to the ancient Greeks, such as Aristotle, who contributed to the definition of the method through what became known as Aristotelian logic, based on the doctrine of syllogism. Afterwards, the deductive method was developed by Descartes, Spinoza and Leibniz.
It is a method of reasoning widely used in scientific research and in several areas, such as Philosophy, Education and Law, as it is related to different ways of reasoning.
See also the meaning of Premise and Syllogism.
Deductive method and Inductive method
The deductive method is usually contrasted with the method that uses induction as the main tool of analysis.
While the inductive method starts from specific cases to try to arrive at a general rule, the deductive method starts from understanding the general rule to arrive at the conclusion of specific cases.
Another important aspect is that, many times, the inductive method leads to an undue generalization of specific cases, which cannot always be considered true. This does not occur in the deductive method, as it uses the process of premises to reach a conclusion.
See more about the Inductive Method and how to write the methodology for the TCC.