Syllogism is a reasoning model based on the idea of deduction, composed of two premises that generate a conclusion.
The forerunner of this line of logical thought was the Greek philosopher Aristotle, known to be one of the first thinkers and philosophers of all time.
The call Aristotelian syllogism it is formed by three main characteristics: mediated, deductive and necessary.
The syllogism would be mediated due to the need to use reasoning to reach the real conclusion. It would be deductive in that one starts from universal prepositions to reach a specific conclusion. And finally, it would be necessary to establish a connection between all the premises.
Learn more about the meaning of premise.
There are several different forms of syllogisms: regular, irregular and hypothetical.
You irregular syllogisms they are abbreviated or extended versions of regular syllogisms, and are subdivided into four categories: entima, epikerema, polysyllogism, and sorites.
- intimate: incomplete syllogism, when there is an implied premise.
- epikerema: extended syllogism, when premises are accompanied by proofs.
- polysyllogism: two or more syllogisms in which the conclusion of the first premises is the preposition of the next syllogism.
- Sorites: an argument composed of four prepositions that are linked together until reaching the conclusion.
There are also the hypothetical syllogisms, which can be: conditionals, disjunctives and dilemmas.
- Conditional: syllogism that neither affirms nor denies the premises.
- Disjunctive: syllogism formed by a premise that presents itself as an alternative.
- Dilemma: argumentative syllogism where two possible hypotheses are presented, none of which is desirable.
See also the meaning of deductive method.
Examples of syllogisms
“All men are mortal. Antonio is a man. Therefore, Antonio is mortal”.
According to Aristotelian thought, the first two premises should come together to form the third idea, which would be the conclusion:
"Every man is mortal" (first premise - major)
"Antonio is a man" (second premise - minor)
“Soon, Antonio is mortal” (conclusion).
See other examples of syllogisms:
“The vertebrate has red blood. The mammal is vertebrate. The carnivore is a mammal. The lion is carnivorous. Therefore, the lion has red blood” (irregular syllogism - sorites).
“Anything that strengthens health is useful. Sport strengthens health. Therefore, sport is useful. Sport is useful. Athletics is a sport. Therefore, athletics is useful…” (irregular syllogism – polysyllogism).
“It is legitimate to kill an unjust aggressor in the face of natural law, positive law and custom. Marcos unjustly attacked Joana: Marcos' background and the circumstances of the crime prove it. So Joana could have killed Marcos. (irregular syllogism - epikerema)
“I think therefore I am” (irregular syllogism – intima)
“If it rains, we don't go to the movies. It rains. So we won't go to the movies” (hypothetical syllogism – conditional).
“This triangle is either isosceles or scalene. Now this triangle is scalene. So this triangle is not isosceles” (hypothetical syllogism – disjunctive).
“The student was either studying or not. If he studied, he deserves to be punished because he did not learn the subject as was his duty; if he didn't study, he also deserves to be punished because he didn't fulfill his duty” (hypothetical syllogism – dilemma).
Syllogism and Sophism
Sophism or sophism is a line of thought or rhetoric that seeks to induce error, based on false logic or meaning.
The sophistic discourse is intended to deceive and, in certain situations, the syllogism may have an intrinsic relationship with the sophism.
The syllogism, even being a logical thought, can generate wrong conclusions, characterizing itself as a sophistical syllogism.
Example: "God is love. Love is blind. Stevie Wonder is blind. So Steve Wonder is God”.
Learn more about the meaning of sophism.
legal syllogism
The legal syllogism is a model of logical thinking that legal professionals (lawyers, judges, prosecutors and etc) perform mainly during the presentation of criminal opinions, by example.
The structure of a legal syllogism would be divided into three stages: the presentation of a major premise, based on the law; the concrete case, that is, the presentation of the facts as they occurred; and, finally, the conclusion that consists in the application of the law to the fact.
For example: "Killing a person is a crime and murder must be punished. Why, John killed someone. Therefore, John must be punished”.
