has many uses in everyday life. Your skill at decides whether the put to you lead you to act well. Spotting a faulty , or an unsupported , could save you from a bad decision.
is how we’ll lay these arguments out, to keep the presentation clean. It makes and easy to point out. It also helps you tell a from an by spotting .
Premise 1: All men are mortal.
Premise 2: Socrates was a man.
Therefore, conclusion: Socrates is mortal.
Not every passage is an argument. A can be built from that have , and still argue nothing, because no part of it is offered in of another. There are eight kinds: , , , , , , , and . Being on that list does not keep a passage out of an argument. It only means the passage is not one on its own.
Explanations are the hard case. An explanation has two halves: the explanandum, the thing to be explained, and the explanans, the thing that explains it. That looks like premises and a conclusion, and sometimes it is — but only when the explanandum is in dispute. If everyone already accepts it, nothing is being argued.
Once you know which kind of argument you have, you can judge how well it holds up. A has when its form guarantees the conclusion, and when it is valid and its premises are true as well. An has when its premises make the conclusion likely, and when it is strong, its premises are true, and nothing important has been left out.
Keep form and fact apart. This is where most people slip. An argument can be valid and still rest on false premises, because validity is a claim about the shape of the argument, not about the world.
Premise 1: All cats are fish.
Premise 2: Konrad was a cat.
Therefore, conclusion: Konrad was a fish.
Valid. If the premises were true the conclusion would have to be — and that is the whole test. Both happen to be false, which is a separate question.
Homework
Reading an argument out of everyday speech and rebuilding it in is the skill the whole chapter builds toward. Tap a sentence to break it into its pieces, assemble each premise and the conclusion word by word, then check your work.
Every argument is either deductive or inductive. The tell is the — the word in the conclusion that reveals which kind of support is being claimed. Read each one, decide which it is, then tap the word that gives it away.
Some passages only give advice, sound a warning, report events, explain a settled fact, or state a condition. Read each one, decide whether it argues anything, and if it does not, name what it is instead.
Now judge them. A deductive argument is valid or invalid; an inductive one is strong or weak. Remember that this is a question of form, not fact — an argument can be perfectly valid and still rest on a false premise.