Logic is the science that evaluates arguments.
An argument is a group of statements including one or more premises and only one conclusion. Essentially, Arguments are made up of premise(s) and conclusions.
A premise is a statement in an argument that provides reason or support for the conclusion. There can be one or many premises in a single argument.
A conclusion is a statement in an argument that indicates what the arguer is trying to convince the reader/listener. What is the argument trying to prove? There can be only one conclusion in a single argument.
You will need to be able to distinguish premises and conclusions:
The simple way to do this is to ask yourself what the author of the argument is trying to get you to believe. The answer to this question is the conclusion.
There must also be at least one reason and possibly many. These are your premises.
Argument vs. Claim vs. Inference
In short, an argument is made up of claims connected by inferences. Each individual step in the argument is a separate claim. There’s a main claim, or “thesis,” which is supported by supporting claims. The supporting claims are intended to respond to doubts about the main claim. Inferences are usually not stated out loud; they are invisible connectors between the claims in the argument.
Types of Argument
To understand the types of argument, please read article on inference
There are two essential types of argument
- Deductive Argument.
- Inductive Argument.
A deductive argument is an argument that is intended by the arguer to provide a guarantee of the truth of the conclusion provided that the argument’s premises are true.
In a deductive argument, the premises are intended to provide such strong support for the conclusion that, if the premises are true, then it would be impossible for the conclusion to be false.
An argument in which the premises do succeed in guaranteeing the conclusion is called a (deductively) valid argument. If a valid argument has true premises, then the argument is said also to be sound. All arguments are either valid or invalid, and either sound or unsound.
The Validity of a deductive argument can be defined in five ways:
- An argument is valid if the premises can’t all be true without the conclusion also being true.
- An argument is valid if the truth of all its premises forces the conclusion to be true.
- An argument is valid if it would be inconsistent for all its premises to be true and its conclusion to be false.
- An argument is valid if its conclusion follows with certainty from its premises.
- An argument is valid if it has no counterexample, that is, a possible situation that makes all the premises true and the conclusion false.
- If x=y, then we can deductively infer that y=x. There’s no way for that not to be true!
- If Socrates is a man and all men are mortal, then Socrates must be mortal as well.
You could always question the premises of a deductive argument (for example, you might say that Socrates is a god, not a man, and therefore question whether he’s mortal), but if you accept the premises you have no logical choice but to accept the conclusion.
An inductive argument is a form of argument in which, if all the premises are true, the conclusion is probably true, but might not be.
Inductive arguments have one crucial advantage: they usually matter more. In our day-to-day life, almost all of our decisions are based on inductive inferences.
- It usually takes me an hour to get to work, so if I leave at 8:00 I’ll probably get there by 9.
- Yesterday I got sick after eating Wendy’s, so I won’t go there for lunch today.
- My best friend advised me not to skip class, and her advice is usually good, so I’ll follow it.
- For the whole history of human experience the sun has risen in the east and set in the west; therefore, the sun will do the same thing tomorrow.