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What is reasonable to hope for from a philosophical argument?

Soundness would be nice -- a true conclusion that logically follows from true premises. But soundness isn't enough. Also, in another way, soundness is sometimes too much to demand.

To see why soundness isn't enough, consider this argument:

Premise: Snails have conscious sensory experiences, and ants have conscious sensory experiences.

Conclusion: Therefore, snails have conscious sensory experiences.

The argument is valid: The conclusion follows from the premises. For purposes of this post, let's assume that premise, about snails and ants, is also true and that the philosopher advancing the argument knows it to be true. If so, then the argument is sound and known to be so by the person advancing it. But it doesn't really work as an argument, since anyone who isn't already inclined to believe the conclusion won't be inclined to believe the premise. This argument isn't going to win anyone over.

So soundness isn't sufficient for argumentative excellence. Nor is it necessary. An argument can be excellent if the conclusion is strongly suggested by the premises, despite lacking the full force of logical validity. That the Sun has risen many times in a regular way and that its doing so again tomorrow fits with our best scientific models of the Solar System is an excellent argument that it will rise again tomorrow, even though the conclusion isn't a 100% logical certainty given the premises.

What then, should we want from a philosophical argument?

First, let me suggest that a good philosophical argument needs a target audience, the expected consumers of the argument. For academic philosophical arguments, the target audience would presumably include other philosophers in one's academic community who specialize in the subarea. It might also include a broader range of academic philosophers or some segment of the general public.

Second, an excellent philosophical argument should be such that the target audience ought to be moved by the argument. Unpacking "ought to be moved": A good argument ought to incline members of its target audience who began initially neutral or negative concerning its conclusion to move in the direction of endorsing its conclusion. Also, members of its target audience antecedently inclined in favor of the conclusion ought to feel that the argument provides good support for the conclusion, reinforcing their confidence in the conclusion.

I intend this standard to be a normative standard, rather than a psychological standard. Consumers of the argument ought to be moved. Whether they are actually moved is another question. People -- even, sad to say, academic philosophers! -- are often stubborn, biased, dense, and careless. They might not actually be moved even if they ought to be moved. The blame for that is on them, not on the argument.

I intend this standard as an imperfect generalization: It must be the case that generally the target audience ought to be moved. But if some minority of the target audience ought not to be moved, that's consistent with excellence of argument. One case would be an argument that assumes as a premise something widely taken for granted by the target audience (and reasonably so) but which some minority portion of the target audience does not, for their own good reasons, accept.

I intend this standard to require only movement, not full endorsement: If some audience members initially have a credence of 10% in the conclusion and they are moved to a 35% credence after exposure to the argument, they have been moved. Likewise, someone whose credence is already 60% before reading the argument is moved in the relevant sense if they rationally increase their credence to 90% after exposure to the argument. But "movement" in the sense needn't be understood wholly in terms of credence. Some philosophical conclusions aren't so much true or false as endorseable in some other way -- beautiful, practical, appealing, expressive of a praiseworthy worldview. Movement toward endorsement on those grounds should also count as movement in the relevant sense.

You might think that this standard -- that the target audience ought to be moved -- is too much to demand from a philosophical argument. Hoping that one's arguments are good enough to change reasonable people's opinions is maybe a lot to hope for. But (perhaps stubbornly?) I do hope for it. A good, or at least an excellent, philosophical argument should move its audience. If you're only preaching to the choir, what's the point?

In his preface to Consciousness and Experience, William G. Lycan writes

In 1987... I published a work entitled Consciousness. In it I claimed to have saved the materialist view of human beings from all perils.... But not everyone has been convinced. In most cases this is due to plain pigheadedness. But in others its results from what I now see to have been badly compressed and cryptic exposition, and in still others it is articulately grounded in a peril or two that I inadvertently left unaddressed (1996, p. xii).

I interpret Lycan's preface as embracing something like my standard -- though with the higher bar of convincing the audience rather than moving the audience. Note also that Lycan's standard appears to be normative. There may be no hope of convincing the pigheaded; the argument need not succeed in that task to be excellent.

So, when I write about the nature of belief, for example, I hope that reasonable academic philosophers who are not too stubbornly committed to alternative views, will find themselves moved in the direction of thinking that a dispositional approach (on which belief is at least as much about walking the walk as talking the talk) will be moved toward dispositionalism -- and I hope that other dispositionalists will feel reinforced in their inclinations. The target audience will feel the pull of the arguments. Even if they don't ultimately endorse my approach to belief, they will, I hope, be less averse to it than previously. Similarly, when I defend the view that the United States might literally be conscious, I hope that the target audience of materialistically-inclined philosophers will come to regard the group consciousness of a nation as less absurd than they probably initially thought. That would be movement!

Recently, I have turned my attention to the consciousness, or not, of garden snails. Do garden snails have a real stream of conscious experience, like we normally assume that dogs and ravens have? Or is there "nothing it's like" to be a garden snail, in the way we normally assume there's nothing it's like to be a pine tree or a toy robot? In thinking about this question, I find myself especially struck by what I'll call The Common Ground Problem.

The Common Ground Problem is this. To get an argument going, you need some common ground with your intended audience. Ideally, you start with some shared common ground, and then maybe you also introduce factual considerations from science or elsewhere that you expect they will (or ought to) accept, and then you deliver the conclusion that moves them your direction. But on the question of animal consciousness specifically, people start so far apart that finding enough common ground to reach most of the intended audience becomes a substantial problem, maybe even an insurmountable problem.

I can illustrate the problem by appealing to extreme cases; but I don't think the problem is limited to extreme cases.

Panpsychists believe that consciousness is ubiquitous. That's an extreme view on one end. Although not every panpsychist would believe that garden snails are conscious (they might think, for example, that subparts of the snail are conscious but not the snail as a whole), let's imagine a panpsychist who acknowledges snail consciousness. On the other end, some philosophers, such as Peter Carruthers, argue that even dogs might not be (determinately) conscious. Now let's assume that you want to construct an argument for (or against) the consciousness of garden snails. If your target audience includes the whole range of philosophers from panpsychists to people with very restrictive views about consciousness like Carruthers, it's very hard to see how you speak to that whole range of readers. What kind of argument could you mount that would reasonably move a target audience with such a wide spread of starting positions?

Arguments about animal consciousness seem always to start already from a set of assumptions about consciousness (this kind of test would be sufficient, this other kind not; this thing is an essential feature of consciousness, the other thing not). The arguments will generally beg the question against audience members who start out with views too far away from one's own starting points.

How many issues in philosophy have this kind of problem? Not all, I think! In some subareas, there are excellent arguments that can or should move, even if not fully convince, most of the target audience. Animal consciousness is, I suspect, unusual (but probably not unique) in its degree of intractability, and in the near-impossibility of constructing an argument that is excellent by the standard I have articulated.

Eric Schwitzgebel