Logic and
Critical Thinking

Philosophy 4

Gale Justin

Critical Thinking involves:

Examining passages that contain pieces of reasoning, called “arguments.” An argument is a group of propositions (or statements). A proposition (or statement) is a claim that is either true or false. In an argument, the propositions have a certain kind of relationship to one another. Specifically, one or more of the propositions is given as a reason to accept the truth of one other proposition.

Here are some arguments:

uBoas make good pets because they are tame and loving animals when properly trained.

uSoda has no nutritional value to athletes as is evident from the fact that they don’t use it before or after games.

uFoundation doesn’t help your appearance, since it clogs pores and increases signs of aging.

In these arguments, one or more statements are offered as reasons to believe one of the other statements is true.

For example, the first two statements are given as reasons to believe the third statement in the argument about foundation. Thus:

uIt clogs your pores.

uIt increases signs of aging.

uFoundation does not help your appearance.

In the other two of the three examples, the “support relationship” is reversed:

u(1) Boas make good pets. (2) They are tame and (3) they are loving animals when properly trained.

u(1)Soda has no nutritional value for athletes as is evident from the fact that (2) athletes don’t use it before or after exercises.

Notice that in both the argument about foundation and the one about Boas, there are two distinct reasons. Take:

u(1) Boas make good pets. (2) They are tame and (3) they are loving animals when properly trained.

uBecause (2) and (3) can stand alone as complete sentences, they are regarded as being distinct reasons.

uIf the reason statement had read: “They are tame and are loving animals,” then for simplicity sake, we would treat the claim as a offering a single reason (when logically speaking it gives two).

Special names are given to the propositions or statements that compose a philosophical argument.

uThe statements that are regarded as offering reasons are called premisses.

uThe one statement that is being recommended on the basis of the reason(s) is called the conclusion.

Arguments always have at least one premiss and always have only one conclusion. But:

uThe order in which the premisses are stated can vary. Premisses can be stated before or after the conclusion. In some cases, some premisses may be stated before and others may be stated after the conclusion.

uTo arrange an argument in standard form, write out the premisses first, draw a line, then write out the conclusion.

For example:

Research assistants are often graduate students, so faculty who do research should not be thought of as shortchanging their students. Moreover, part of the money for the research project often goes to the university.

In standard form, the latter argument looks like this:

Premiss: Research assistants are often graduate students.

Premiss: Part of the money for the research project often goes to the university.

_______________________________

Conclusion: Faculty who do research should not be thought of as shortchanging their students.

Here’s another argument in standard form:

Premiss: Only the A’s and the Angels can win the West.

Premiss: The A’s have a better pitching staff than the Angels.

Premiss: The A’s have more home games for the rest of the season than the Angels have.

---------------------------------------------------------

Conclusion: Only the A’s can win the West.

Here’s another example of standard form:

Premiss: As head of FEMA Bush appointed a lawyer with no background in emergency management.

Premiss: Clinton’s FEMA head was a man with 15 years of public safety experience.

__________________________________

Conclusion: George Bush makes less competent appointments than Bill Clinton made

When reading a passage, the best way to begin the process of extracting its argument is to identify the conclusion. That is,

uAsk yourself first “What am I supposed to believe as a result of reading this passage?” Whatever that is, that is likely to be the conclusion.

uThen identify the premiss(es) by asking “What reasons are given for me to believe that the conclusion is ture?”

Moreover, there are certain words or phrases that flag the premiss(es) or the conclusion of an argument.

uPremiss indicators include: since, for, given that, on the grounds that, insofar as, as indicated by. (See p. 12 for a longer list.)

uConclusion indicators include: thus, so, therefore, hence, it follows that. (See p. 12 for a longer list.)

Now do some groupwork on distinguishing premisses from the conclusion of an argument.

In the arguments we have just examined, notice some features of the premiss(es) offered in support of the conclusion.

uThe premiss is “directly known” whereas the conclusion is “inferred” or “indirectly known” on the basis of the reasons.

uA premiss is a consideration which is independent of the conclusion. It does not simply restate in different words what the conclusion states.

To explain:

uThe premiss “Valuables are missing” is directly known whereas “It was apparently burgled” is an inference that is made partly on the basis of having observed the absence of the valuables.

uThe premiss “Valuables are missing” is a consideration which is independent of the conclusion that “It has been burgled.” The premiss could be true, even if the car had not been burgled. For example, Steve may simply have forgotten to put them in the car. So the conclusion is not just repeating the premiss. It says something different from the premiss.

Consider this argument:

u(1) There is indeed a god of some sort. (2) We can explain the creation of the universe with the Big Bang theory but we need a cause to explain the Big Bang itself.

uNotice that (2) is based on what we know directly, namely, that events have causes. So it is in a sense “directly known” or at least “better known” than the conclusion. Also, (2) could be true without (1) being true. So (2) is independent of (1). (2) is not just restating or assuming the truth of (1).

But consider this argument:

u(1) There is indeed a god of some sort. (2) For God created the world.

uNotice that (2) is not either “directly known” or“better known” than the conclusion. Also, (2) could not be true without (1) being true. So (2) is not independent of (1). Thus, this is not a good argument. It is said to “beg the question.”

To sum up:

uThe premisses are known generally speaking on the basis of either your own observation or someone else’s testimony. The conclusion is “indirectly known” or “inferred from” the premisses.

uThe premisses state circumstances that are independent of the conclusion in the sense that they would be the case, even if the conclusion was not true.

Note:

uThis point about the conclusion being indirectly known on the basis of the premisses is important.

uWe will come back to it.

One further point about arguments is worth noting. This is the fact that speaking generally again, two kinds of claims show up as the conclusion of an argument.

uReports of investigations

uRecommendations

Consider again the earlier examples from your groupwork:

u“I bet Pat is the smartest person in the class,” “It was apparently burgled,” and “Busby can’t have set the fire,” are reports of investigations.

u“Euthanasia should not be legalized,” and “There should be stop sign at First and Richmond” are recommendations.

The use of language to support the conclusion of an investigation or to make a recommendation is, however, only one use of language.

uLanguage can be used to express feelings. This is called its “expressive” use.

uLanguage can be used to give orders. This is called its “directive” use.

uLanguage can be used to describe various kinds of things. This is called its “descriptive” use.

Before we do some groupwork, take note of your homework.

For Homework:

uMake a copy of page 6 of your logic text book.

uOn that copy, identify the premiss(es) and the conclusion of the arguments in passages #2-15.

uTo do this, bracket the conclusion and put a “C” at the opening bracket. Then bracket the premiss(es) and put a “P” at the opening premiss bracket.

Identify premiss statements that contain both a subject and a predicate as a single premiss (see #17).