# Arguments and Explanations

30.01.2018

Episode #5 of the course Logic basics: Understanding arguments by Gary Curtis

In yesterday’s lesson, we talked about using premise indicators to identify the premises of arguments. Today, you’ll learn how to tell arguments from explanations.

Argument vs. Explanation

It’s easy to confuse arguments and explanations, since explanations, like arguments, are made up of statements. Also, explanations often use the same indicator words and phrases used in arguments. The difference between them has to do with the purpose each serves:

argument: a piece of reasoning whose purpose is to provide evidence for its conclusion

explanation: a piece of reasoning whose purpose is to make its conclusion more predictable or understandable

Reasoning can be used for many purposes, and providing evidence that a certain statement is true is only one. Other reasoning aims to give a reason or reasons why a certain statement is true; such reasoning is an explanation.

One reason why it’s necessary to draw this distinction is that explanations frequently use the same indicator words as arguments. So, if you rely solely upon indicator words to identify arguments, you’ll mistake some explanations for arguments.

How to Tell the Difference

How can you tell the difference between an argument and an explanation? Since the difference is one of purpose, ask what purpose a piece of reasoning serves. If it gives evidence that a statement is true, then it’s an argument. If it gives reasons why it’s true, then it’s an explanation.

There is no mechanical test for telling whether a piece of reasoning is an argument or an explanation, so you need to use your understanding of the meaning of the passage as a whole and your sense of the author’s purpose. Test your understanding of the difference with the following examples.

Examples: Both of the examples below are from Stephen Hawking and Leonard Mlodinow’s A Briefer History of Time (2005).

• “Today we know why the planets take such unusual paths across the sky: though the stars hardly move at all in comparison to our solar system, the planets orbit the sun, so their motion in the night sky is much more complicated than the motion of the distant stars.” (p.8)

This is an explanation, and one clue is the wording at its beginning: “Today we know why the planets take such unusual paths across the sky.” The word “why” is a tip-off that the following sentence is an explanation of the more complicated motion of the planets as compared to that of the stars. The authors are not trying to convince you that the planets move differently than the stars, but to explain why they do so. That the planets move differently than the stars was known since antiquity from observation, so it did not need arguing but explaining. What explains it is the fact that “the planets orbit the sun,” whereas the stars do not, though the latter fact is not mentioned because it’s assumed that you already know it.

• “In 1609, Galileo started observing the night sky with a telescope, which had just been invented. When he looked at the planet Jupiter, Galileo found that it was accompanied by several small satellites or moons that orbited around it. This implied that everything did not have to orbit directly around the earth, as Aristotle and Ptolemy had thought.” (p.10)

This is an argument and not an explanation. There is one conclusion indicator in this passage, namely, “this implied that,” which shows that the conclusion is, “everything did not have to orbit directly around the earth.” The authors are giving Galileo’s reasoning that led to the revolutionary conclusion that not everything in the universe revolves around the earth. The premise for this conclusion is in the preceding sentence, namely the fact that Jupiter has moons. This is not an explanation because the fact that Jupiter has moons in no way explains why not everything orbits the earth, it only establishes that it is true. Moreover, in Galileo’s time, it was assumed that everything in the universe did indeed revolve around the earth, so this claim needed evidence rather than an explanation.

In tomorrow’s lesson, you’ll put explanations aside for the duration of these lessons and learn about the distinction between two types of arguments: inductive and deductive.

Recommended book

An Introduction to Non-Classical Logic: From If to Is by Graham Priest

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