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In logic, an argument (Latin argumentum - "proof, evidence, token, subject, contents") is a connected series of statements or propositions which are intended to provide support, justification or evidence for the truth of another statement.
A deductive argument asserts that the truth of the conclusion is a logical consequence of the premises; an inductive argument asserts that the truth of the conclusion is supported by the premises. Deductive arguments are judged by the properties of validity and soundness. An argument is valid if and only if the conclusion is a logical consequence of the premises. A sound argument is a valid argument with true premises.
For example, the following is a valid argument (because the conclusion follows from the premises) and also sound (because additionally the premises are true):
- Premise 1. All Greeks are human.
- Premise 2. All humans are mortal.
- Argument. Take an arbitrary Greek. By premise 1 this Greek is human; by premise 2 this human is mortal. Thus, this arbitrary Greek is mortal.
- Conclusion. Therefore, all Greeks are mortal.
Invalid arguments involve several fallacies that do not satisfy the idea that an argument must deduce a conclusion that is logically coherent. A common example is the non sequitur, where the conclusion is completely disconnected from the premises.
Not all fallacious arguments are invalid. In a circular argument, the conclusion actually is a premise, so the argument is trivially valid. It is completely uninformative, however, and doesn't really prove anything.
From the source
An odd way of looking at arguments, and possibly how not to do them properly, is the following sketch:
M: I came here for a good argument.
A: No you didn't; no, you came here for an argument.
M: An argument isn't just contradiction.
A: It can be.
M: No it can't. An argument is a connected series of statements intended to establish a proposition.
A: No it isn't.
M: Yes it is! It's not just contradiction.
A: Look, if I argue with you, I must take up a contrary position.
M: Yes, but that's not just saying 'No it isn't.'
A: Yes it is!
M: No it isn't!