Identifying the Conclusion and All the Premises

§2.2

Once you are confident that you have found an argument, you need to identify its premises and conclusion. In order to recognize that a passage contains an argument in the first place, you must have already noticed that at least one proposition is intended either to support or to be supported by another. Thus, you will have already identified either a conclusion or a premise. Now you need to identify any remaining premises or conclusions that there may be. In doing this keep in mind that they may be introduced with inferential particles, but that they needn’t be.

The argument may be presented in any order. For example, each of the sentences expresses the same argument as the map on the right.

Map 9:

(i) Alcohol should be illegal, because it’s a drug and all drugs should be illegal.

(ii) Alcohol is a drug, and all drugs should be illegal, so alcohol should be.

(iii) All drugs should be illegal, so alcohol should be, since it’s a drug.

In (i), the conclusion is written first, followed by the two premises; in (ii) the conclusion is written after the premises; and in (iii), it is placed in between them.

To ensure that you have found all of the premises and the conclusion, read through the passage carefully, focusing separately on each proposition—each claim that could be expressed as a separate sentence (however it is actually formulated in the passage as written). Then ask yourself why the proposition is there. Is it intended as a part of the argument or as some sort of aside? If it is part of the argument, then what role is it playing: is it meant to be supporting some conclusion, or to be supported by some other proposition?

If you are having trouble figuring out whether one proposition is intended to support another or to be supported by it, it can help to ask yourself which proposition is more obviously true? In arguments we try to establish propositions that we are less sure of by inferring them from ones that we are surer of.