The Structure and Purpose of Argument

The purpose of an argument for a critical thinker is not to win, although that is often the default mode of how we behave. Often, we pick a side and then defend that side at all costs, marshaling whatever arguments we think can defend that position.

The critical thinking approach to argumentation is to value the process of developing your arguments and reaching conclusions; a critical thinker should be willing to change any conclusion when new information or a better argument is presented.

Rationalizing is the process of starting with the conclusion and then figuring out which arguments can be marshaled in order to defend that conclusion. On the other hand, reasoning focuses on the process going forward, where the conclusion flows from the logic and not the other way around.

Often, we use the rationalizing process, which can seem very superficially similar to reason. In fact, the point of rationalizing is to make it seem as if our decisions and conclusions are reasonable.

When we have a conclusion that is discordant—that is not in line with the facts or is challenged by a new argument or new piece of

information—our tendency is to rationalize that new information in order to resolve the cognitive dissonance that results, and then our brains reward us for doing that.

To avoid cognitive dissonance, we should focus on the process instead. In other words, if we don’t tie ourselves firmly to a conclusion, then we won’t feel any emotional dissonance when new data is encountered that shows that the conclusion is wrong.

Specifically, in logic, the term “argument” is a set of statements used to support a conclusion. An argument must start with specific premises and then logically derive a conclusion from those premises. Explanations and assertions are not arguments.

A premise is a starting point; it is a fact or assumption that we take as a given at the beginning of an argument. If a premise is false, then any argument that is based upon that premise is not sound. Therefore, it’s very important to examine all of the premises and to recognize what the premises of an argument actually are. Often, that is a missing step in an argument.

Assumptions can be used as premises, but we need to recognize when we are starting with a statement that is not an established fact. It is not known whether an assumption is true; it might be incomplete and might not fully capture the whole situation. Assumptions or incomplete premises weaken an argument because the argument is only as good as the premises on which it is based.

When two or more people disagree over a factual statement, one side or both sides must be wrong in some way. By definition, two mutually exclusive conclusions can’t both be correct at the same time.

The goal should be to examine both of your arguments to find out where the assumptions are in the premises, where the false premises are, or where the errors in logic are. If you can work together to discover the errors and assumptions of logic, then you should be

able to resolve your differences and come to a better conclusion.

If a claim is true, it is factually correct; it is in line with reality. Arguments themselves are not true or false; their conclusions are true or false.

In most cases, we do not have access to truth with metaphysical certitude, so what we’re really looking for is something that is established to a sufficient degree that we can treat it as if it were a fact, although we know that all true statements are tentative in some way because they are dependent upon our incomplete current level of knowledge.

If the logic works, then an argument is valid. One or more premises may still be wrong or unjustified, but an argument fails when it is impossible for the conclusion to be false if the premises are true.

An argument is sound when all of the premises are true and the logic is valid. The conclusion of a sound argument, therefore, must be true by definition; if the premises are true, then the conclusion must also be true.

The conclusion of an unsound or invalid argument, however, may or may not be true. Demonstrating that an argument is unsound or invalid does not prove the conclusion to be false—it just removes that argument as justification for the conclusion.

Deductive reasoning uses premises to connect to a conclusion. Deduction goes from the general to the specific. You start with some general statements, and then you deduce a specific instance that must be true if those general statements are themselves true.

For example, if premise one is that all men are mortal and premise two is that Socrates is a man, then we can arrive at the conclusion that Socrates is therefore mortal.

Conclusions of deductive reasoning are positive assertions. They are truth statements—not value judgments, which involve subjectivity regarding what we believe. For example, there is no way to prove that Beethoven’s music is better than Mozart’s. Oftentimes, arguments involve one or more value judgments in the premises, and when you identify them, you can at least agree to disagree.

In contrast to deductive reasoning, inductive reasoning goes from a specific observation to a general principle. Inductive reasoning is used to decide what is probably true based on observations. Science is largely based on inductive reasoning.

For example, if premise one is that every swan that has ever been observed is white, we may come to the inductive conclusion that all swans are white. However, this statement is falsifiable; the observation of a single black swan will render the statement untrue. Then, the statement might have to be modified to the notion that most swans are white or, perhaps, that all swans except for the species of black swans are white.

Logical fallacies are arguments in which the conclusion does not have to be true if the premises are true. The generic term for this type of invalid logic is the non sequitur, which literally means “it does not follow”—or the conclusion does not follow from the premises. Essentially, logical fallacies are our mechanisms for rationalizing conclusions.

The argument from authority is a logical fallacy that typically suggests that a conclusion is correct because an authority figure asserts that it is correct. The more general form is that a conclusion is correct because a person or a group making the claim have some positive or admirable attribute. For example, John says it’s true, and he’s a nice man; therefore, his conclusion must be correct.

We have this evolved desire to get along with the social group and to follow a leader of some sort, and we therefore have this tendency to respect celebrities, officials, experts, and professionals—people who have some claim to authority.

The argument from authority can also be overapplied, meaning that we can dismiss legitimate arguments by the claim that they are arguments from authority. In other words, because the argument from authority is a logical fallacy, that doesn’t mean that we should be dismissive of the value of the consensus of expert opinion.

Another logical fallacy is the argument from final consequences. The form that this fallacy typically takes is that some claim cannot be true if it results in consequences that you find abhorrent; the opposite of this fallacy is that something is true because it serves a positive purpose.

We often see this argument in conspiracy theories, for example. The logic that often goes into conspiracy theories is the principle of cui bono, or “who benefits.” If an event occurs, the conspiracy theorist might ask, “Who benefited from this event?” Then, they would argue that, therefore, that person must have caused the event through some hidden conspiracy.

A very common logical fallacy is called post hoc ergo propter hoc: “after which hence by which.” We tend to assume that if B follows A, therefore A must have caused B.

This logical fallacy derives from innumeracy, a naivety about statistics and probability. We are impressed with the pattern that B followed A, and we instinctively don’t like the explanation that the occurrence is a statistical fluke or just random chance. We like to impose meaning on the patterns that we see.

Very similar to this is confusing correlation with causation, in which the form of the argument is not just that B follows A, but that B correlates with A. Where we see B, we also see A. The assumption, therefore, is that A must cause B. However, this is not logically the case. It’s possible that B causes A. It’s also possible that some other factor, C or D, causes both B and A. This also assumes that the correlation is real and not a coincidence.

Similar to the argument from authority, the logical fallacy of assuming causation from correlation can be overapplied to dismiss the very legitimate significance of a correlation. Once we establish that a correlation is real, that doesn’t mean that there’s no causal relationship between the two things. It means that there are a number of possible causal relationships, one of which may be the simplest one: that A causes B.

Another logical fallacy is special pleading, which is also called ad hoc or post-hoc reasoning, meaning that we invent reasons as needed in order to explain certain aspects of the evidence. This logic is not formally invalid. The fallacy occurs in the process of invoking these arguments after we know that they’re needed to crudely construct a problematic conclusion.

This kind of logic may be a way of generating a hypothesis but can’t be used as a premise or conclusion to dismiss inconvenient evidence or the absence of evidence that should be there.

The special pleading fallacy is related to the fallacy of limited scope, which involves introducing a new element that is not a broadly applicable principle. It narrowly addresses a single flaw in evidence or argument.

This type of argument has been invoked frequently to explain why there is no evidence of the existence of Bigfoot. Some have argued that perhaps he can turn invisible, travel through other dimensions, or disappear when needed to—and that’s why you can never trap him.