The Structure Of An Argument

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By aaron

One of the most important concepts in critical thinking is the concept of argument structure. By understanding the structure of an argument, you will be better equipped to find mistakes in a line of reasoning, whether it is yours or someone else's. So let's have a look at the structure of an argument.

An argument consists of two main components. The first component is the premise, or premises if there are more than one. The premises are facts, observations, and assumptions on which an argument is based. The second component is the conclusion, which is basically the result of the argument, which you arrive at after considering all of the premises.

Here is a common example argument that demonstrates this:

All men are mortal. Socrates is a man. Therefore, Socrates is mortal.

This argument has two premises. The first premise is that all men are mortal. The second premise is that Socrates is a man. In other words, these are facts and observations that the argument is based on. After taking those premises into consideration, we arrive at the conclusion that Socrates must be mortal.

In this particular example, both of the premises are explicitly stated, although that is not always the case. In most cases, one or more premises of an argument will not be explicitly stated. For example, we could rephrase our example argument like this:

Socrates is mortal because all men are mortal.

This is the same argument, but in this wording we don't explicitly state the premise that Socrates is a man. That fact is assumed to be given, so it is still a premise of the argument even though it isn't stated in the argument itself. Then, using that premise along with the premise that all men are mortal, we arrive at the same conclusion: The conclusion that Socrates is mortal.

Now that we have covered premises, let's look more closely at the argument conclusion. I want to clear up some confusion between two terms that are frequently used interchangeably, but are in fact different. Specifically, I want to look at the difference between argument validity and argument soundness.

If an argument has correct logical structure, it is said to be valid. Being valid does not mean that the argument is true, it simply means the logical structure makes sense and-- as long as the premises are all true-- then the argument would be true.

Here is an example of an invalid argument:

If it rains, the streets will be wet. The streets are wet. Therefore, it rained.

This argument is not valid, because the logic itself is wrong. The conclusion will never necessarily be true regardless of whether or not the premises are true. Even if is true that rain would cause the streets to be wet, and even if it is true that the streets are wet now, that still doesn't mean it rained, because there are many other reasons the street could be wet.

Consider this slightly different example that is logically valid:

It if rains, the streets will be wet. It has rained. Therefore, the streets are wet.

This argument is valid because if it is true that rain causes the street to be wet, and if it is true that is has rained, then it is necessarily true that the streets are wet. But again, that is only if those premises are true.

If an argument is valid and all of the premises are true, then the argument is said to be a sound argument. A sound argument will always be a valid argument. Recall the first example argument I gave:

All men are mortal. Socrates is a man. Therefore, Socrates is mortal.

This argument if valid because it makes logical sense. In addition, both of the premises are true. Because it is valid and the premises are true, this is a sound argument.

When there is a mistake that causes an argument to be either invalid or unsound, you have what is known as a fallacy. And that will be the topic of the next lecture. Thank you for listening! #logic #skepticism #critical thinking #fallacy #fallacies

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