An argument is a set of statements in which some, the premises, support another, the conclusion. And a good argument needs two things at once: true premises and a valid structure. Confusing these two things is the origin of half of the discussions that no one can explain why they lost.
What is an argument
In everyday life, "argument" has become synonymous with fight. But in the technical sense, an argument is the link between premises and conclusion through an inference, the word "therefore". The two thousand year old example: all men are mortal; Socrates is a man; therefore, Socrates is mortal. The first two statements are premises; the third is the conclusion, and the "then" is the hinge where all reasoning lives.
Understanding this changes the nature of a discussion: it stops being a dispute over who speaks loudest and becomes an exchange of reasons that can be examined.
Truth is not validity
This is the most valuable distinction in all of informal logic. Validity is just the fit of the structure: if the premises were true, would the conclusion follow from them? Truth is the content: do the premises really match reality? And the decisive point is that these two things vary independently of each other.
You can have a perfectly valid structure with false premises: all fish fly; salmon is fish; therefore, the salmon flies. The form is impeccable, and the conclusion is absurd, because the first premise is false. And it goes the other way: reaching a true conclusion through invalid reasoning, which is not thinking, it is guessing by luck.
This appears outside of logic books too. Think of an ad: "Successful people wake up at five in the morning, so if you wake up at five, you will be successful." The premises may even be true, but the "logo" is crooked: it confuses what only accompanies success with what causes it.
When an argument is solid
An argument is only solid when it brings together two things: true premises and valid structure. If any one of them is missing, reasoning may even convince, but it is not knowledge, it is the appearance of knowledge. And these rules do not belong to anyone: the laws of valid reasoning are universal, in the same way that the multiplication table does not change from person to person.
With this distinction in hand, you can now see most of the errors in reasoning that previously you could only feel in your stomach without knowing how to point them out. The next step is to name the most common disguises that this error assumes, the logical fallacies, and understand why logic does not exist to win arguments, but to seek the truth.
Readings from Nous
Read the classics in depth
Our list of more than 130 recommended books, commented and organized by theme, so you don't read in the dark.
See recommended readingsFrequently asked questions
What is an argument, in logic?
It is a set of statements in which some, the premises, support another, the conclusion. The classic example: all men are mortal; Socrates is a man; Therefore, Socrates is mortal.
What is the difference between truth and validity?
Validity is the fit of the structure: if the premises were true, would the conclusion follow? Truth is the content: do the premises match reality? The two vary independently.
Can an argument be valid and still wrong?
Yes. "All fish fly; salmon are fish; therefore, salmon fly" has a perfectly valid structure and an absurd conclusion, because the premise is false. Only an argument with true premises and a valid structure is solid.
Continue in the cluster of this class: What is a premise · What is a syllogism · Difference between truth and validity
Home class (Training in Philosophy and Theology): Ferramentas do Pensamento Crítico