Identifying & Evaluating Arguments

Gig Φ Philosophy
(at-a-glance overviews of philosophical concepts)

Published September, 2022

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Identifying Arguments

WHAT TO LOOK FOR?

Having introduced what an argument is, as well as its constituent parts, it will serve us well to look at some of the differences between arguments and nonarguments. Identifying arguments may not always be easy, but being able to do so, along with discerning which parts provide support for the conclusion, is an important task in logical reasoning. Arguments can be simple or complex, they can be clearly stated or muddled. Even more problematic, is that nonarguments can often appear quite similar to arguments, and thus be used in their place, rather than having to really provide support for a claim.

Be sure to ascertain if something is being supported. An argument, again at its most basic level, must provide reason(s) for thinking that some statement is true. If the passage is not doing this, then there is no argument present. To that end, it might be helpful to look at examples of nonarguments to make our concept of argument even clearer.

NONARGUMENTS

Notice that the following, though they may appear to give us reason to think that something is the case, in fact merely exclaim, or tell us how or why something is the case. The following are all examples of nonarguments [Hurley (2018), pp. 17-22]:

EXAMPLE NONARGUMENTS

WARNINGS: Express danger or alert us to pay special attention, not necessarily providing reason to think that such danger exists.
ADVICE: Express recommendations for belief or behavior, without necessarily providing reason to accept the advice.
BELIEFS: Express attitudes towards propositions of acceptance, rejection, or neutrality; without necessarily providing reason to agree.
OPINIONS: Express attitudes of judgment or preference, without necessarily providing reason to agree.
STATEMENTS: Though constitutive of arguments, may simply be loosely joined by a similar subject matter, without necessarily providing support for any other statement.
REPORTS: Similarly to loosely joined statements, may merely express information about something.
EXPOSITIONS: Express greater detail about some statement or subject, without necessarily providing reason to establish the thing being elaborated on.
ILLUSTRATIONS: Express instances or examples of some statement or subject, without necessarily providing reason to establish the thing being illustrated.
EXPLANATIONS: Express descriptions of some event or phenomena, without necessarily providing reason to establish that the thing being explained has occurred.
CONDITIONALS: If […] , then [...] Express statements where one part (the consequent) depends upon another part (the antecedent) to hold. They lay out the conditions under which some event or phenomena would hold, without establishing that either conditions actually hold.
DISJUNCTIVES: Either [...] , or [...] Express statements where two or more potential options are provided. They lay out the options available, without establishing if either or both actually hold.

It is worth noting that all of the above instances, though insufficient in and of themselves to be arguments, can all be utilized within arguments should they be accompanied by support.

DEDUCTIVE ARGUMENTS

Now that we have seen and discussed the topic of arguments it would help us to make a key distinction between argument types. Traditionally, philosophers and logicians have identified two types of arguments: deductive and inductive. A deductive argument is an argument that intends to make the conclusion follow necessarily from the premise(s). Here is an example:

EXAMPLE DEDUCTIVE ARGUMENT

P1. All musicians are entertainers.

P2. Lizzo and Regina Spekter are musicians.

C. ∴ Lizzo and Regina Spekter are entertainers.

In deductive arguments the intention is that if the reasons (or “premises”) are true, then the conclusion must be true. The truth of the premises is meant to establish or guarantee the truth of the conclusion. To determine if the argument is deductive, we can ask ourselves: do the premises attempt to prove the truth of the conclusion?

INDUCTIVE ARGUMENTS

By contrast, a nondeductive, or inductive argument is an argument that intends to make the conclusion likely or probable given the premise(s). The distinction between “necessary” and “likely or probable” conclusions is meant to capture the difference between deductive and inductive arguments. The intention of inductive arguments is that if the reasons (or “premises”) are true, the conclusion is only probably true. The truth of the premises is not meant to establish or guarantee the truth of the conclusion, but only make it more likely. Here is an example:

EXAMPLE INDUCTIVE ARGUMENT

P1. Most musicians are entertainers.

P2. Lizzo and Regina Spekter are musicians.

C. ∴ Lizzo and Regina Spekter are [probably] entertainers.

Here, we can see that even if the premises are true, the conclusion could still potentially be false. To determine if the argument is inductive, we can ask ourselves: do the premises attempt to increase the likelihood of the truth of the conclusion?

Notice the difference between the previous argument and this subtle alteration:

In the first case, the conclusion is intended to follow with necessity from the premises. That is, if we accept that “All musicians are entertainers” and that “Lizzo and Regina Spekter are musicians” then what follows is that “Lizzo and Regina Spekter are entertainers”.
However, the use of the word 'most' in the second argument leaves open the possibility of the conclusion being false.

Both kinds of arguments are used not just in philosophy, but in fields like mathematics, science, and law, just to name a few. It is imperative to understand how each type of argument attempts to guarantee the truth of its conclusion in order to best assess the strength of the arguments one is making or considering.

Evaluating Arguments

You may have noticed that the aforementioned definitions for deductive and inductive arguments state that they each merely attempt to establish the truth or likelihood of their conclusions, respectively. Here we must note that not all arguments are successful. One of the most significant skills to take away from studying logic and becoming a critical thinker is being able to identify good and bad arguments. Bad reasoning does not establish what it attempts to, and thus, we should not be convinced by it. This does not necessarily mean that the conclusion is false, but that better reasoning is required for it to be established.

VALID ARGUMENTS

A deductive argument that succeeds in proving its conclusion is said to be valid. In a valid deductive argument, it is impossible for true premises to lead to a false conclusion. In other words, the structure of the argument guarantees the truth of the conclusion. To be clear, validity is not grounded in an argument's verified “truth” in the world. Validity merely refers to the necessity of the conclusion's truth if the premises are true. Again:

EXAMPLE VALID ARGUMENT

P1. All women are mortal.

P2. Hypatia is a woman.

C. ∴ Hypatia is mortal.

This argument is valid. It is impossible for the premises to be true and the conclusion false. In other words, if it is true that “all women are mortal” and that “Hypatia is a woman”, then it must be true that “Hypatia is mortal”. However, this says nothing about the actual truth of these premises (perhaps the “Hypatia” being referred to is my cat, and not the Ancient Greek philosopher).

INVALID ARGUMENTS

When a deductively valid argument fails to succeed in guaranteeing the truth of its conclusion, it is said to be invalid. In an invalid deductive argument, it is possible for the premises to be true, and the conclusion false. Now let us examine the following argument:

EXAMPLE INVALID ARGUMENT

P1. All logic instructors are smart.

P2. Rebeka is smart.

C. ∴ Rebeka is a logic instructor

Although the structure is similar to the valid argument in the previous example, here, the conclusion certainly does not follow from the premises. That is, it is possible for the conclusion to be false, even if the premises are true.

SOUND ARGUMENTS

Once we have determined that we are dealing with a deductively valid argument, we need to determine whether or not it is sound. An argument is sound if and only if it is the case that it is valid and all of the premises are actually true in the world.

HELPFUL HINT SOUNDNESS

Sound Argument =
Deductively Valid + All True Premises

Both criteria are important since, as we can see, truth alone is not enough. It is a mistake to say that an argument is a good one simply because its premises and conclusion are true. Consider this argument:

EXAMPLE UNSOUND ARGUMENT

P1. San Francisco is a city in California.

P2. Seattle is north of San Francisco.

C. ∴ it rains in Seattle.

Even though every statement in the above argument is true, we could not say that this is a good argument. In order to be sound, not only must the premises all be true, but the conclusion must follow from the premises.

Finally, it should be noted that given its reliance on the measurability of objective reality; we may not always be in an epistemic position to determine an argument's soundness. Whether or not one is inclined towards skepticism, humanity’s technological advancements cannot keep pace with our myriad metaphysical beliefs.

STRONG ARGUMENTS

As discussed in the previous section, unlike deductive arguments, an inductive argument cannot guarantee that if its premises are true, the conclusion will also be true. Even though inductive arguments are not truth-preserving, this does not mean that they cannot still succeed in providing sucient support for their conclusion. An inductive argument that succeeds in making its conclusion more likely to be true than false is said to be strong. Here is an example of a strong inductive argument:

EXAMPLE STRONG ARGUMENT

P1. Most Star Wars fans dislike Jar Jar Binks.

P2. Rebeka is a Star Wars fan.

C. ∴ Rebeka dislikes Jar Jar Binks.

WEAK ARGUMENTS

Likewise, if an inductive argument fails to make its conclusion more likely to be true than false, it is said to be weak. Here is an example of a weak inductive argument:

EXAMPLE WEAK ARGUMENT

P1. Some movie theaters are showing Get Out every evening this week.

P2. There is a movie theater down the street from my house.

C. ∴ the movie theater down the street from my house is showing Get Out tonight.

To aid in determining whether or not an inductive argument is strong or weak, the following indicator works are worth noting:

EXAMPLE INDUCTIVE INDICATOR WORDS

STRONG

most

often

almost all

Usually anything indicating more than > 50% likelihood

WEAK

a couple

few

some

Usually anything indicating less than < 50% likelihood

COGENT ARGUMENTS

As we saw with validity for deductively valid arguments, strong inductive arguments with true premises are said to be cogent.

HELPFUL HINT COGENCY

Cogent Argument =
Inductively Strong + All True Premises

Even though inductive arguments do not guarantee the truth of their conclusions, even when cogent, it is of great import to establish the likelihood of their success. Induction happens to be the primary means by which we come to know the workings of the empirical world, and is thus one of the bases of scientific reasoning.

KEY POINTS: DEDUCTIVE VALIDITY

VALID = If the premises are true, then the conclusion must be true.
INVALID = If the premises are true, and the conclusion could still be false.
Validity only applies to deductive arguments, not inductive arguments.
Validity refers to the form or structure of the argument, not its content.

Take the following example:

EXAMPLE VALID ARGUMENT

P1. All men have five arms.

P2. Anthony is a man.

C. ∴ Anthony has five arms.

This argument is valid, even if premise 1 is obviously false. So in order to assess the content of deductive arguments, we need another criterion.

KEY POINTS: INDUCTIVE STRENGTH

STRONG = If the premises are true, then the conclusion is more likely to be true (than false).
WEAK = If the premises are true, and the conclusion is more likely to be false (than true).
Strength and weakness only apply to inductive arguments, not deductive arguments.
Strength can be subjective†, but no matter how strong an inductive argument is, it can never guarantee the truth of its conclusion.

Take the following example:

IS THIS A STRONG ARGUMENT?

P1. You are undergoing medical procedure X.

P2. Medical procedure X has a 75% success rate.

C. ∴ you will have a successful medical procedure.

Although 75% is a rather high likelihood of success, in cases where the stakes are high (say, life and death), some might require a higher bar for strength (say, at least 80-85%). For lower stakes content, some may find any likelihood over 50% to be sufficient. However, given the nature of inductive reasoning, even if the success rate was 99.999%, there is never a guarantee that the next instance will be successful.

Ref. Henderson, Leah. "The Problem of Induction". The Stanford Encyclopedia of Philosophy. (Spring 2020)

INFERENCE TO THE BEST EXPLANATION

Two primary points of concern for philosophers and logicians with respect to inductive reasoning revolve around its use in explanation, prediction, and confirmation. Obviously, there are many problems with justifying a conclusion based solely on probability. For example:

Are we ever justified in moving from a nite number of past observations to predictions about all future observations?
How many past observations do we need to make before using them as evidence for universal scientific claims?

As critical thinkers, we want strong, well-supported arguments, without making hasty generalizations. Thus, we always want to be careful when arguing about groups as a whole based on a small sample.

Inductive reasoning is also deployed when attempting to determine the most likely explanation for a given phenomena. A common method used for this in science and criminal justice is Inference to the Best Explanation [IBE], where the most likely explanation is asserted as the actual explanation.

However:

What if our determination of the “best” explanation was selected from wholly bad explanations to begin with?

Surely it being the best is by no means any indication that it is true. Just because one has devised an explanation for something does not mean it's the right one. Other explanations, perhaps yet to be considered, could be just as good. (van Fraassen, p. 143)

Finally, as with general problems with induction: IBE always goes “beyond the evidence”.

It tries to explain facts, but does so by positing a theory that is not derived entirely from those facts.

AT-A-GLANCE
Identifying & Assessing Arguments

Identifying & Evaluating COMPLEX Arguments

While the main focus of this text is formal logic, some may find themselves wondering what to do when arguments / reasoning are so complex that they do not fit into any of the syllogistic forms discussed above. Given that entire courses are dedicated to more informal types of reasoning, we will only gesture towards how the skills we’ve been developing could apply to presenting, explaining, and evaluating complex arguments. The method outlined below is appropriately named, “The PEE Method”:

See here for more detailed instructions on presenting, explaining, & evaluating an argument

See here for more detailed instructions on presenting one's argument in deductively valid form

See here for more detailed instructions on explaining one's argument

See here for more detailed instructions on defining technical terms in one's argument

See here for more detailed instructions on providing rationales for one's argument

See here for more detailed instructions on evaluating one's argument