Some claim that the philosophy is just the practice of making and assessing arguments. I deny this claim, as evidenced in my earlier post, “Philosophy Without Argument.” Nonetheless, argumentation is an important, probably essential, component of philosophy. What does it mean to argue, and what does it mean to argue well?

Good Arguments 

What makes a good argument? First off, an argument is a passage made up of at least two statements, one of which (called the conclusion) the author intends to show is true on the basis of the other statements (called the premises). A statement is a declarative sentence; in other words, a claim that is either true or false. “Augustine once stole pears,” “It is morally wrong to steal fruit,” and “God exists” are all statements. Note how each is either true or false. The sentences, “Did Augustine once steal pears?” “Suppose that it is morally wrong to steal fruit,” and “God exists?!” are not statements. Note how none is either true or false. Here’s an example of an argument:

Augustine once stole pears. It is morally wrong to steal fruit. Therefore, Augustine once acted immorally.

How does one evaluate an argument? The famous first line of Tolstoy’s Anna Karenina goes like this: “All happy families are alike; each unhappy family is unhappy in its own way.” Similarly, all cogent arguments are cogent in the same way. Two and only two conditions must be met: the argument must have good CONTENT and it must have good FORM. Good content means its premises are true, and good form means that the truth of the premises actually support the truth of the premises. Thus, a cogent thinker is able first to evaluate the truth of statements as objectively as possible; and second, to determine the truth relationship between two or more statements. It is also worth noting that these tasks should be performed independently of each other.

Consider this analogy. Say that you want to make a good sausage with a machine. You need good meat going in and the machine in good working order. If you put in good meat, you will get good sausage. Good pork, good bratwurst. Note, also, that whether or the meat is good or not has nothing to do with the working order of the machine. And whether the machine is in working order has nothing to do with the quality of the meat.

What do you think of the above Augustine argument? Here’s my take. Regarding the first premise, there’s reasonable evidence that Augustine did steal pears on at least one occasion. He himself confesses to this deed, plus there’s no good reason to doubt his veracity on this matter. To quote Book 2 of his Confessions: “There was a pear tree close to our own vineyard, heavily laden with fruit, which was not tempting either for its color or for its flavor. Late one night—having prolonged our games in the streets until then, as our bad habit was—a group of young scoundrels, and I among them, went to shake and rob this tree.” As for the second premise, whether the morality of actions is determined by goods valuable to humans, rights claimed and given, duties to others, or by the weight of consequences, taking the property of others without their voluntary, informed consent, namely, stealing, is morally wrong. Now, given that pears are a kind of fruit, if the premises are true, then it follows that the conclusion is also true. So, since both premises are probably true, and the conclusion is logically supported by the premises, I think that the Augustine argument is fairly cogent. Note also that my evaluation of the argument’s content was performed independently of my evaluation of its form.

Pear Tree by Klimt

Regarding content—that is, the truth of the premises—focus on the evidence for and against, and, if there are those with expertise on the given content, determine what those experts say and listen to them. Of course, this approach to evaluating content is nothing new. It was articulated by Socrates in the Theaetetus, among other Platonic dialogues. (See below.*) Now, I make clear to my students that I am not the authority on non-philosophical matters. If there is a question that clearly belongs to the domain of psychology—for example, “Is there such a thing as ESP?”—then study psychology or speak with a psychologist. Also, I tell students to drop the “how do we know anything?” attitude typical of philosophical novices. Reserve such questions for a class dedicated to epistemology. Or, I tell them, catch me outside of class time. To do ethics, for instance, you shouldn’t be caught up in the fog of skepticism, fun as it may be, and you need to get your facts straight. Doing philosophy in any useful, meaningful manner requires some minimal understanding of the world we live in. For example, people are starving in developing nations and those living in developed nations are partly causally responsible for this starvation. Fact. (Now, if you want to dispute this fact, go for it. Just not on my time.) Recognizing this, we can then move to the next question, which is an ethical one: Are those in developed nations partly morally responsible for assisting these starving people?


The basic idea behind good form is that your accepting the premises should convince you to accept the conclusion, or at least be more inclined to accept the conclusion. In other words, the premises actually support the conclusion.

To put this another way, imagine again a reliable sausage machine. If you put good meat into the machine, you are most likely to get good sausage. This is what an argument with good form does (though with statements, not meat!). For example:

All cats purr. Rocket is a cat. Therefore, Rocket purrs.

Now, you don’t know whether Rocket really is a cat. (He is, but you don’t know that.) Nor is it obvious that all cats purr. I once had a cat that just grunted. Nevertheless, when it comes to form, these questions are irrelevant. The question is this: If you deny the conclusion, can you still accept the premises? In this example, the answer is no. If Rocket doesn’t purr, then at least one of the premises is false.

Consider a variation on the Rocket theme where the argument clearly has bad form:

All cats purr. Rocket purrs. Therefore, Rocket is a cat.

It’s important to realize that arguments that have true premises (that is, good content) can still have bad form. Here’s an example of one:

Guinness is a kind of beer. Some beer is made with wild yeast. Therefore, Guinness is made with wild yeast.

Also, arguments can have good form yet have false premises (that is, bad content). Here’s an example:

All cheese is blue. Everything blue is moldy. Therefore, all cheese is moldy.

Apart from intuition, how does one determine that an argument has bad form? There are several methods, but for now just consider what I call the “counterexample technique.” To begin, understand that a form of reasoning cannot be good if it moves from true premises to a false conclusion. Consider the following argument:

If that bar serves Guinness, then the Irish will come. That bar doesn’t serve Guinness. Therefore, the Irish will not come.

Now, intuitively this argument appears to possess bad form. For even if both of the premises are true, Irish customers might come for other reasons. Perhaps the bar serves Murphy’s Irish Stout. Or perhaps they will come on “Thistle & Shamrock” nights.

But there’s another way to show that it’s invalid. First, figure out the form of the argument. Here it is:

If G then I. x is not G. Therefore, x is not I.

But isn’t there at least one argument of the same form that has true premises and a false conclusion? And since there is one, the Guinness argument has bad form. Here’s a counterexample of the same form:

If cats are dogs, then cats are animals. Rocket the cat is not a dog. Therefore, Rocket is not an animal.

To sum up: To employ the counterexample method of showing that an argument has logically bad form, produce another argument of the same form (a “substitution instance”) with obviously true premises and an obviously false conclusion.

Take another example. Consider the following argument from Harry Potter and the Deathly Hallows, p. 229:

Everyone from Magical Maintenance wears navy blue robes. That bloke wears navy blue robes. Therefore, that bloke is from Magical Maintenance.

Intuitive: Even if everyone from Magical Maintenance wears navy blue robes, perhaps people from other departments in the Ministry of Magic also navy blue robes. That possibility has not been ruled out. To refute this argument using a counterexample, however, you need to find the form of the argument. It goes like this:

All M are N. x is N. Therefore, x is M.

Now, here’s a counterexample of the same form but with clearly true premises and a clearly false conclusion:

All dogs are mammals. My cat Rocket is a mammal. Therefore, Rocket is a dog.

It should now be clear that the original Harry Potter argument has bad form. Not surprisingly, it is Ron Weasley who offers this lousy argument. It is surprising, however, that Hermione failed to catch his mistake. Perhaps she was in love.

There is much more to be said about arguments, including the different kinds of arguments—deductive/inductive, a priori/a posteriori, etc.—but what’s said above is a start.

How does Socrates respond to Protagorean relativism?

Socrates certainly agrees with Protagoras that “[m]ost things actually are, for each person, the way they seem to him or her, for instance hot, dry, sweet, or anything of that sort.” In these kinds of cases at least, appearances constitute reality and knowledge is just perception. However, “if there are any questions on which it will concede that one person is superior to another, it will be about what’s healthy and unhealthy….” It is simply false that every human “knows what’s healthy for itself and is capable of curing itself.” Socrates also argues that “matters that concern the state” are also not relative to the individual. One city manager can be better and wiser than another.

So while it is reasonable to think “man” is the measure of immediate, intimate things, this is not true of future things. In such cases, some people judge more accurately than others. Relativism cannot account for experts: doctors, vintners, athletic trainers, cooks, lawyers, etc. A layman is certainly not a better judge than a vintner “when it’s a question of the future dryness or sweetness of wine.” And what makes the vintner’s judgment more accurate and authoritative is not because the vintner said so, but because the vintner understands some absolute truths about grape vines, water, weather, and land.

So humans are the measure of some things but certainly not all things.


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