Consistency is very important in the deductive method.
The deductive method is a scientific method that considers that the conclusion is implicit within the premises . This means that the conclusions are a necessary consequence of the premises: when the premises are true and the deductive reasoning is valid, there is no way that the conclusion is not true .
The first descriptions of deductive reasoning were made by philosophers in Ancient Greece , including Aristotle . It is worth noting that the word deduction comes from the verb to deduce (from the Latin deducĕre ), which refers to the extraction of consequences from a proposition.
Characteristics of the deductive method
The deductive method is able to infer something observed from a general law. This differentiates it from the so-called inductive method , which is based on the formulation of laws based on the facts that are observed.
In research using the deductive method, hypotheses are therefore developed based on existing theories. The aim is to test the hypothesis in question by analysing the implicit link between the theories and specific cases.
There are those who believe, like the philosopher Francis Bacon , that induction is preferable to deduction , since it allows us to move from particulars to something general.
The deductive method can be direct proof or indirect proof.
Tools to consider
When appealing to the deductive method, a series of tools and instruments are usually used to achieve the proposed objectives of reaching the required point or clarification, always considering that the thought goes from the general to the particular .
In this sense, we can say that summaries are frequently used, since they are the documents that allow us to concentrate clearly and concisely on the essentials of a subject. However, it should also be noted that synthesis and synopsis are also used.
But the list of procedures and tools goes much further. Thus, maps , graphs , diagrams and demonstrations could not be ignored. The latter in particular help to demonstrate that a principle or law is true, and to do so, all established truths as well as logical relations are used as a starting point.
The deductive method is used in social sciences and formal sciences.
Types of deductive method
The deductive method can be divided according to whether it is direct and of immediate conclusion (in cases where the judgment is produced from a single premise without any other premises intervening) or indirect and of mediate conclusion (the major premise contains the universal proposition, while the minor includes the particular proposition: the conclusion, therefore, is the result of the comparison between both).
Other classifications refer to types of deductive method such as modus ponens (which indicates that if S is true and S implies T, then T will be true), modus tollens (if S implies T and T is not true, then S is not true either) and syllogism (the conclusion is reached by starting from two assumptions that share a term in common with what is given as a result).
In all cases, researchers who use the deductive method begin their work by establishing assumptions (consistent with each other) that merely incorporate the main characteristics of the phenomena. The work continues with a procedure of logical deduction that ends with the statement of general laws .
Advantages and disadvantages
Scholars of philosophy and epistemology list various advantages of using the deductive method in research. It is argued that this method stands out for its usefulness when testing a hypothesis .
On the other hand, the deductive method contributes to the measurement of concepts in a quantitative way and to the generalization of results . It is even claimed that it can be developed more quickly compared to other methods.
As for its disadvantages, it must be considered that deductive reasoning allows to guarantee the validity of the argument, but cannot ensure the falsity or truth of the conclusion because it is not oriented to the content, but to the argumentative formality.
A logical fallacy , in this context, arises when an argument is constructed using the deductive method based on false or erroneous premises. For example, if one starts with the premise that Americans speak English and then states that John speaks English , one might conclude that John is American . However, that conclusion may be wrong.
Examples of deductive method
Among the examples that we can use to understand more exactly what the concept of deductive method means would be the following: if we start from the statement that all English people are punctual and we know that John is English , we can conclude by saying that, therefore, John is punctual .
Let's look at another example. Starting from the axiom that dogs are animals that have four legs and bark and knowing that Firuláis is a quadruped animal and communicates by barking , it is possible to say that Firuláis is a dog .
In the field of mathematics, the deductive method is also widely used. Thus, in this subject we can find examples that demonstrate this, such as this one: if A is equal to B and B is equal to C , we can determine that A and C are equal .