3. More about claims and premises
We said earlier that an argument must have at least one claim and one premise. However, some arguments contain only hidden premises. Consider the argument:
8. The best way to avoid getting AIDS is to simply not have sex.
This is an argument with a single, hidden premise, namely, ‘having sex is the main way of getting AIDS.’ As we have said, when the premise is, or seems to be, uncontroversial, premises may not be stated. It is assumed in 8. that everyone agrees with the hidden premise and that the claim can be inferred from it. Whether you accept the conclusion or not will depend partly on whether you accept the hidden premise; however, you could accept the premise and still argue that there is a better way to avoid getting AIDS. As we shall see in later posts, words, like ‘best’ carry a lot of implicit content.
Be aware that sometimes something that looks like an argument is not an argument at all, but an explanation or description. You must be clear about the differences between these functions. As we have said, an argument must have a claim and at least one premise (even if hidden), but another way to characterise arguments is in terms of their function.
Thinking along these lines, we can think of an argument as a way of persuading someone that a statement is true or correct. Usually, an argument tries to convince someone to believe something new or different whereas a language function like explanation is an answer to a ‘Why?’ question – in other words, a request for further information or clarification. Explanations are commonly used to make something that is already accepted clearer or more understandable. Consider the difference between
9. Why does the Sun come up in the morning? (you already believe it, but you want to know how it happens). Explanation: The sun appears to come up in the morning because the Earth revolves around the Sun. If you are standing on the Earth, the Sun would appear to move in relation to your position.
and
10. Why should I believe that the Sun comes up in the morning? (You have lived your whole life in a cave and have never seen the sun). Argument: The sun comes up in the morning. If you were to go outside of your cave, you would observe a bright orange globe that rises over the horizon at the start of each day.
REVIEW
• An argument must have a claim and at least one premise
• One, more, or all the premises of an argument could be implicit
• Arguments whose premises are entirely implicit are usually uncontroversial
• Arguments can be distinguished from other language functions by thinking about their purpose: the purpose of an argument is to convince somebody of something they do not yet believe.
Try Exercise 3 to test your understanding of this and earlier posts, or continue reading…
Essential Thinking for Philosophy 
9 should be revised above. The earth revolving around the sun explains the seasons. The earth rotating about its central axis or spin axis (axis that enters/exits the north and south poles and extends though the center of mass) is what explains the apparent rising and setting of the sun.