Logic

What makes an argument "good"? Is there more to a good argument than raw persuasive power? Does a good argument have to support the right conclusion? For example, might the ontological argument be a good argument for theism even if theism is false?

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This is a deep and interesting question, which goes to the heart of what exactly the point of philosophy is. Let's begin, however, by fixing some ideas about arguments. Arguments may be either valid or invalid; sound or unsound. An argument is valid if and only if the conclusion of the argument is a logical consequence of its premises; an argument is sound if and only if it is a valid argument with true premises. So, for example, the following argument is valid: (1) All green ideas sleep furiously; (2) This idea is green; (3) Therefore, this idea sleeps furiously. (This example is derived from Noam Chomsky, who used the phrase 'Colorless green ideas sleep furiously' in order to illustrate that competent English speakers could recognize a meaningless sentence as grammatical.) Obviously--I would claim--the preceding argument, although valid, is not sound, because ideas aren't colored and they don't sleep (except in the most metaphorical of senses). By contrast, the following argument is both valid and sound: (1) All humans are mortal; (2) Socrates is a human; (3) Therefore, Socrates is mortal. Now most philosophers are quite competent at producing valid arguments (although there are exceptions: Hobbes, for one, was notoriously muddled about modal notions, which led him to propose invalid arguments regarding freedom in Leviathan): what's at issue, however, is whether those arguments are sound. The ontological argument, for example, certainly seems to be valid: (1) The concept of God includes all perfections; (2) Existence is a perfection; (3) Therefore, God, a perfect being, necessarily exists. What's at issue, however, is whether the argument is sound. This question turns on the status of premise (2): is existence indeed a perfection? The argument seems to presuppose that existence is a predicate just like any other predicate, for example, powerful. But is existence a predicate? Philosophers such as Kant and Frege have denied this, and, consequently, have concluded that the ontological argument is not sound. Of course, in order to advance this claim, these philosophers have to give an alternative account of what existence is, an account that proponents of the ontological argument might well reject. (And, of course, proponents of the ontological argument might reject the rather rough-and-ready sketch that I gave of it in favor of a more subtle rendering of the argument, on the grounds that only the rough-and-ready sketch is vulnerable to such objections, whereas in its more refined version, it is not vulnerable in this way.) Even if, however, one maintains that the ontological argument isn't sound, one might nevertheless maintain that it is a good argument--that is, a subtle, interesting argument, a good piece of philosophy--even if it ultimately fails to prove its conclusion and hence is unsound. Indeed, it seems to me that one distinctive feature of philosophy is that even if one disagrees forcefully with some argument--and such disagreement is at the heart of philosophy--one may nevertheless recognize that the argument in question is a good one, that is, a good piece of philosophy. Hence one sometimes--perhaps not often enough, but that's another matter--hears philosophers say that some argument is clever but completely wrong. So one might, therefore, recognize an argument as a good argument, yet fail altogether to be persuaded by it, because one disagrees with some premise that is required for the argument to be sound. This brings out a distinctive feature of philosophical argumentation: it aims to persuade by giving reasons in support of a claim. In this respect, philosophy differs from rhetoric, which aims to persuade by any means necessary, as it were. Hence, for example, the Greek Sophists were accused of teaching their students mere rhetorical tricks, designed to persuade, despite being indifferent to the truth. (The Sophists, in certain respects, may be seen as the ancient predecessors of contemporary political consultants.) Plato, in numerous of his dialogues, engages with the Sophists, and thereby seeks to distinguish philosophy, as the pursuit of truth through rational argumentation, from rhetoric, which took raw persuasive power as a good in itself.

The term 'good' is notoriously ambiguous. However, I often tell my students that a goal for their arguments should be that an intelligent, well-informed person with no strong pre-existing opinion on the matter would find it convincing. Thus, a 'good' argument could have a conclusion that is ultimately false. And it is possible for 'good' arguments to exist for logically incompatible conclusions. Note, however, that there is more to this account of a 'good' argument than pure persuasive power... it has to be persuasive to a certain kind of person (whereas some arguments that 'persuade' the masses are not particularly convincing to the well-informed or the intelligent).

As for the ontological argument, I don't think it is a good argument (in the sense above) in contemporary culture because most people would not find its premises to be more likely than its conclusion (and generally the point of an argument is to get someone to accept a conclusion based on the strength of its premises and their connection to the conclusion). However, there may have been older worldviews (such as the Platonic worldview) where claims like 'existence is a perfection' would be viewed as very likely to be true. Thus, in that context the ontological argument would be better than it is in our contemporary context.

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