We explain what a premise is, its function in reasoning, differences between major and minor premises, and various examples.
What is a premise?
In logic and philosophy, premises are called the initial propositions of an argument, from which it is possible to reach a conclusion. The latter must be inferred or derived from the former, through a deductive or inductive procedure that is valid, that is, forming a valid, logical argument.
This word comes from Latin praemissus, “Previously sent”, constituted in turn by prae- (“before and miter (“Send” or “throw”), so that it has always made reference to what is given in advance, what is initially owned.
Likewise, the premises are the starting point of a reasoning, that is, that which we already know or that has been told to us or has been given to us, and from where our deductive work begins. The clues, figuratively, that a detective has to gather to reach a certain conclusion, that is, the antecedents, the hypotheses.
The study of premises dates back to classical antiquity, when the great Greek and Roman thinkers studied logic and oratory as forms of thought, generally around the syllogism: a certain type of reasoning in which given two premises, one general and another particular one, a conclusion is obtained.
Since they are propositions, the premises always affirm or deny something, which can be of a general or particular nature, and therefore they can be true or false. This affirmation or denial is expressed in terms of a sentence, such as “In the Caribbean the climate is hot” or “All planets are round” or “No pig can fly.”
It is not the truth or falsity of the premises, however, that determines whether the reasoning is valid or not, since true conclusions can be inferred from false premises.
The nature of the argument or reasoning depends on the relationship between the premises and the conclusions. For example, deductive reasoning draws a particular conclusion from general premises, while inductive reasoning goes in the opposite direction.
There are, in addition, reasoning with a single premise or several, and even some that require additional premises in order to reach a conclusion.
Premise types
According to the Greek Aristotle (384-322 BC) in his studies of the syllogism, there are two types of premises involved in this type of logical reasoning: the major premise and the minor premise.
- The major premise it is usually of general type, and contains the predicate of the conclusion. A general proposition is one that refers to a set or totality of certain things, for example: “All men are mortal.”
- The minor premise it is usually of a particular type, and contains the subject of the conclusion. A particular proposition is one that refers to a specific thing or subject, for example: “John is mortal.”
However, there are other types of premises, such as the implicit ones, that are not mentioned or are understood, as in the case of: “All men are mortal and Juan died yesterday”, in which it is not necessary to specify that Juan is a man.
Examples of premises
Some examples of premises are the following:
Major premise: All birds have beaks.
Minor premise: A hen is a bird.
conclusion: All chickens have beaks.
Major premise: No mammal can breathe underwater.
Minor premise: Whales are mammals.
conclusion: No whale can breathe underwater.
Major premise: The sun shines.
Minor premise: The sun is a star.
conclusion: The stars shine.