Philosophy of religion, as practiced by religious believers, is often confused with apologetics. (Perhaps it is even so confused, on occasion, by some of its practitioners.) Indeed, if we use the term 'apologetics' more broadly, to include not just the giving of an apologia (defense) of religion, but of just any belief system, then we could say that philosophy in general is often confused with apologetics. This is, I think, a serious mistake. The philosopher, qua philosopher, is up to something quite different than the apologist, qua apologist. The 'qua' clauses are necessary, because of course the same person may engage in both philosophy and apologetics and, as will emerge, it is even possible to do both at the same time, but as activities they have fundamentally different aims. I will try, in this post, to clarify this difference and explain why it matters.
My take on the subject is influenced by the discussion of the nature and aims of natural theology in the first chapter of Ross's Philosophical Theology, where Ross distinguishes between the aim of establishing a conclusion and convincing people of a conclusion, but I will not follow Ross too closely, and I will especially not adopt his very odd (quasi-Aristotelian) usage of the words 'science' and 'scientific'.
Let's start with apologetics. What the apologist would really like to do is to give arguments which will actually convince a particular audience who does not already believe the conclusion that the conclusion is true. This, of course, is a tall order, especially when it comes to anything so contentious and practically and emotionally important as religion. The apologist might, therefore, be willing to settle for less. She may instead be happy if she can give arguments which will cause the members of the audience to increase their credences in the conclusion. Note that if the apologist has this second aim, then there is a point to her activity even if her audience consists only of people who already accept the conclusion, for she may aim only to make those who are, e.g., already Christians more confident that Christianity is rationally justifiable. The point, however, is that the aim of the apologist (qua apologist) is to give to a particular audience arguments which will have a particular effect on them.
This, I claim, is not the aim of the philosopher (qua philosopher). The philosopher aims instead to discover arguments which are such that people holding certain views (which real people do, or at least are likely to, hold) will, upon considering the arguments, be rationally obligated to endorse the conclusion. Thus the philosopher differs from the apologist in two ways: first, in that the philosopher aims to discover arguments, rather than just to give them to people, and, second, the philosopher is not concerned with what will actually convince people, but only about what people rationally ought to be convinced by. Two further notes are in order on this point. First, the philosopher need not be thought of as trying to discover arguments which no human being has ever thought of. My primary research is in early modern philosophy; I'm just as happy to find an argument in the library as to think it up on my own. Second, we need here a notion of rational obligation or the rational ought on which one is not rationally obligated to endorse the logical consequences of one's view unless and until one considers an argument demonstrating those logical consequences. In other words, we need an account of the rational obligations of beings (like us) who are not logically omniscient. Giving such a theory is, of course, notoriously difficult.
Now, the philosopher's ideal aim is, again, a tall order, for in nearly all (if not absolutely all) cases it is rationally permitted to reject a premise rather than accepting the conclusion. The philosopher may therefore retreat to the weaker aim of discovering arguments the consideration of which obligates people to revise their views in some way or other, even if it leaves open more than one option for the revision. Again, if we can't achieve even this, we may feel we have still accomplished something if we discover arguments which obligate people to revise their credences in some way, even if they are not obligated to make any changes in what they outright believe.
In sum, the apologist is engaged in what could (depending on one's attitude to the apologist in question) be classified either as a public education campaign, or a propaganda campaign. The philosopher, on the other hand, is engaged in a research program. This difference is the fundamental one; it is for this reason that the apologist is concerned with whether people actually accept his arguments, but the philosopher is concerned only with whether people are rationally obligated to accept hers. Of course, an apologist might be (and in my view ought to be) principled and so refrain from trying to get people to accept arguments which they rationally ought not to accept, but this would be a moral constraint on the apologist's activity, and not part of the aim of that activity.
It's worth asking, if this is the case, why do philosophers bother publishing, and why do they care whether other philosophers accept their arguments? The answer in both cases is that philosophy, like other research programs, is a cooperative activity. The philosophical community as a whole is engaged, together, in trying to discover these arguments. This necessitates sharing proposed arguments and engaging, together, in the evaluation of them, and attaching at least some weight to the evaluation given by others.
Finally, what does this mean for the relationship between philosophy and apologetics? Well, the obvious answer is that, if the apologist adopts the principle of only trying to get people to be convinced by arguments they rationally ought to be convinced by, then the apologist is really a popularizer of philosophy. (Of course, if the apologist is not principled in this way then he may also attempt to pass off arguments rejected by philosophers, or just make emotional appeals or use other means not having to do with reason.) This, furthermore, is why I said earlier that it is possible to engage in both activities at once, especially if philosophers are the target of the apologia. That is, one may publish one's arguments both as part of the cooperative research program and in the hope of actually convincing one's fellow researchers. (Or, in an increasingly popular trend, one may publish a book in which one tries to address both one's fellow philosophers and the educated public at once.) The fact that a particular individual has both aims may effect her mode of presentation, but this need not interfere with doing good philosophy. However, it seems to me that in this kind of case the philosophy is going to constrain the apologetics a lot more than the other way around. The philosopher, for instance, must be engaged in the project of trying to figure out exactly who rationally ought to be convinced by the argument, and this may lead the philosopher to point out ways of escape from the argument which, qua apologist, she might wish could go unnoticed. But this again is something which, in my view, the principled apologist ought to do anyway (and, indeed, perhaps from a moral perspective, though not from the perspective of achieving one's ends, it is even more important for the apologist to do this, since the apologist speaks to non-experts who are less likely to discover the way of escape for themselves).
Although philosophy and apologetics may go together, it is comforting to the philosopher that they need not. Being concerned only with the rational force of arguments, the philosopher may ignore the vagaries of human psychology, or of social pressures regarding belief, because, if these are the reasons the argument is not accepted, then the philosopher may nevertheless have succeeded at her aim of giving an argument which rationally ought to be accepted.
(cross-posted at blog.kennypearce.net)