"The aim of argument, or of discussion, should not be victory, but progress."
— Joseph Joubert

An argument is any statement that is meant to convince others that something is a good idea to believe in.

In logic, an argument is a series of statements called propositions that support a conclusion. For example:

Believing in things you can't justify is illogical.
Jane believes that God doesn't exist but cannot justify this belief.
Therefore, Jane is illogical.

In this example, the first two lines are propositions that support the conclusion in the last line.

Types Of Arguments

In logic, there are two main types of arguments: deductive and inductive. A sound deductive argument results in a true fact. An inductive argument however, can only result in a conclusion that has a probability of being true.

Deductive Arguments

In deductive arguments, the conclusion logically follows from the premises.

Validity

A deductive argument is valid when, if all the arguments premises were true, then the conclusion would have to be true. If the premises were true but the conclusion could be false, the argument is invalid.

Soundness

A deductive argument is sound when all the argument's premises are true and the conclusion is true.

Here is an example of an invalid and unsound argument:

All men are immortal. (false)
Plato is a man. (true)
Therefore Plato is mortal. (true)

The argument is invalid because the conclusion does not follow from the premises. The argument is unsound because the first premise is false.

Here is an example of an valid and unsound argument:

All hammers are red. (false)
Plato is a hammer. (false)
Therefore, Plato is red. (false)

This argument is valid because if the premises were true, the conclusion would be true. The argument is unsound because both the premises and the conclusion are false.

Here is an example of an valid and sound argument:

All men are mortal. (true)
Plato is a man. (true)
Therefore Plato is mortal. (true)

Inductive Arguments

An inductive argument involves making a generalization based on what is known or observed. Here's an example of an inductive argument:

Every swan I have ever seen has been white. Therefore most swans are probably white.

Generally speaking, science is a form of inductive reasoning. Suppose you are interested in a question like "Do psychedelics have health benefits?" Any evidence you uncover that shows a health benefit of psychedelics would make that question more likely to be true. Any evidence showing adverse health effects would make that question less likely to be true.