It depends on what you want to do with your knowledge of mereology. The Department of Philosophy at the University at Buffalo (State University of New York) is a world center for research on applications of ontology to artificial intelligence and informatics, and much of their work is based on various theories of mereology. For further information, link to "Areas of Study: Ph.D. with a focus in Ontology" (where you'll also see an old photo of me if you scroll down the page :-) That page also has links to the National Center for Ontological Research.

There were actually quite a lot. For instance, there were the Neoplatonists, around the third century, such as Plotinus, Proclus and Porphyry. Then there were the Fathers of the Christian Church, from the third to the fifth centuries. Some of the latter, it is true, do qualify more as theologians than philosophers: but there were also several genuine philosophers among them, such as Origen, Tertullian or Saint Augustine. After that, though, the state of philosophy in this region (and we're talking about the Mediterranean here, from Greece and Rome, through Asia Minor, down to Egypt) did begin to decline. Boethius (d. 524 or 525) is sometimes cited as the last significant philosopher of the classical period, before the Dark Ages properly set in. And I do know what you mean, because then there was quite a striking gap in philosophical activity. The gap might not have been a thousand years, but it probably was two or three hundred. Still, though, things did eventually start to get back on track; and the location of the important work shifted too. The ninth century, for instance, brought us John Scotus Eriugena, who originated in Ireland and worked in France. And the ninth and tenth centuries also brought us the early developments in Arabic philosophy, with people like Al-Kindi and Al-Farabi in Baghdad.

Now, as to why philosophy should have ebbed and flowed in this way, declining in one place and arising in another, that's an interesting enough question: but it's not a philosophical question. Why did the Roman Empire decline and fall in the fifth century? Why were the marauding Goths and Vandals so successful in their destructive rampage? Why did grand new civilisations subsequently begin to emerge in the Middle East and in North-Western Europe? Much ink has been spilt, attempting to answer these questions from the perspective of political history. And I would suggest that, whatever answer that research might yield, regarding the rise and fall of empires in general, exactly the same answer is also going to explain the rise and fall of philosophy. Although there have always been clever people around, it's only been when such people have been sustained by a stable and prosperous society that they've had the leisure to indulge themselves in cloistered abstractions. If you want to find philosophers, look for flourishing civilisations. If there are none of those around, there won't be any philosophers either.

How does anyone (not just philosophers or other academics) justify a choice of profession? One does what one is good at and what one likes to do.

Academics in particular (philosophers included) need not apologize for their choice; we are, after all, teachers (in addition to being [perhaps] ivory-towerish scholars or researchers), and teachers surely serve the greater good. We philosophers, in particular, encourage critical (and skeptical) thinking, which--I suggest--is a Good Thing even if what we critique might be whether or not material objects are mereological sums of simples (or something equally esoteric).

Some of us do try to help solve practical problems (and Karl Marx once observed that philosophers have only tried to understand the world but that the point is to change it--I would imagine those are fighting words to some, inspiring to others!). Yes, my analysis of Wittgenstein or, more obscurely, Meinong might not directly improve people's lives, but then again how would we prove that? Maybe my analysis of Meinong in a course might inspire some student to further study of philosophy and that might lead in turn to her studying artificial intelligence (yes, there is a link!--see some of my own publications :-), which might lead to some breakthrough in applications of AI to medicine.

I'm too tired to answer this directly. But if I had nothing else to say, I'd insist that art---painting, sculpture, music---has as little "direct" contribution to make as does philosophy, and I'm quite convinced of the importance of art to human flourishing. So perhaps the answer should be, "Man does not live by bread alone". Which is not, of course, to say that bread isn't important.

Answer to Q1: Why should a person who loves philosophy not steer towards academic philosophy? The better one knows her the more she has to offer, such as fascinating arguments. Answer to Question 2: If you are in love with someone, you really should marry that person, other things equal, no? Philosophy can be difficult sometimes, even temperamental, but she is not mad.

Right after the secret handshake...

More seriously, there's no single answer, and no clear one in any case. Does someone who has a BA in philosophy count as a philosopher? How about someone who has no formal education in philosophy, but through lots of reading and informal conversation has gotten good at the sorts of things philosophers do?

Sufficient conditions are not so hard to come by. Someone who regularly publishes in recongnized philosophy journals would count. So would anyone who regularly teaches bread-and-butter philosophy courses in a university philosophy department. But not all philosophers publish, and not all teach.

Necessary conditions aren't hard to come by either. Someone who had poor verbal skills and neither has nor ever had any talent for thinking analytically wouldn't count as a philosopher. But there are many linguistically gifted analytically-skilled thinkers who aren't philosophers. (An excellent lawyer, for example.)

There are some useful generalizations, of course. Philosophers typically have studied philosophy in university. In any case, they generally have a wide acquaintance with and a good understanding of philosophical texts and ideas. They are interested in certain sorts of questions, though there's a fair range of possible interests and aversions here. (One philosopher might be fascinated by questions about the foundations of morality but have no taste for theory of knowledge; another might have more or less the opposite preferences.)

The most promising answer may seem like a cheat at first: you become a philosopher when you've reached the point where philosophers would agree that you are a philosopher. In one way, this begs the question: it assumes without giving a deeper story that there are already some people who count as philosophers, and it bootstraps from there. But there's no cure for that; "philosopher" isn't a natural kind, marked out by some reasonably tight set of defining characteristics. There are, however, many paradigm examples. (All members of this panel, for instance, are philosophers by any reasonable accounting.) And there are reasonably well-defined formal and informal practices, networks, associations and the like that philosophers recognize and that recognize philosophers, as it were. (Publishing in certain journals, belonging to certain associations, having certain educational backgrounds, working on certain problems...) On the one hand, all this is still fuzzy around the edges. (For example: there are academics who have all their training outside of philosophy and aren't employed by philosophy departments, but who have made valuable contributions to the field. Are they philosophers or not? There's no sharp answer.) But on the other hand, there are people who have an amateur and sometimes crankish interest in philosophy and who think of themselves as philosophers. Most of the people who count as philosophers by all reasonable measures would disagree. Surely that should carry some weight!

The suggestion here is hardly original, and would work in a good many other cases: mathematician, historian, chocolatier, chef, musician... I might be able to knock together a few pieces of wood to make a bookcase. The guy who's rebuilding my porch, however, wouldn't count me as a carpenter, and since he clearly is a carpenter, his opinion is worth a lot more than mine.

So when do you become a philosopher? Not at any one moment, but gradually, as you reach the point where philosophers count you as one of their own.

Yes, there surely are (just look through the list on the right), though it's probably also true that women are better represented in practical philosophy than in philosophy generally. Outside practical philosophy, among the earliest in this country was Ruth Marcus who taught Saul Kripke, among many others, and had a very distinguished career at Yale. Leigh Cauman (even earlier) studied with Quine, taught logic, and was the managing editor of the Journal of Philosophy for many years. Women are very strongly represented in ancient philosophy, with Gisela Striker (Harvard) a good example. In the history of modern philosophy there's Beatrice Longueness (NYU) . If you look through the various departments -- www.philosophicalgourmet.com/overall.asp -- you'll find that most of them have one or more female philosophers outside practical philosophy, so examples could be multiplied. While the profession is still a long way from where we should and want to be, further progress is made likely by there already being a substantial female presence in most areas of philosophy.

Oh, good graduate students most certainly make contributions: they get good papers published in good journals. And if that doesn't count as "making a contribution", then very few of us make contributions. (Our students make contributions in another important way too: they teach their teachers, keep us enthused, prompt better work from us too.)

Of course, few pieces published by graduate students make stunning advances: but then few pieces published by anyone make stunning advances (in philosophy or in any other discipline).

I don't know (and my guess is that my co-panelists don't either.) That, I'm assuming is why it's taken so long for anyone to respond even with such a useless answer. But in defense of myself and my colleagues, most people who belong to a profession, I'd guess, have a relatively scant knowledge of the institutional history of the profession. For example: most physicists probably don't know when or where the first university physics department was established, most dentists probably don't know where the first dental school was, most insurance brokers probably don't know what the first insurance company was, and so on.

I forgot to add: There is a long and extremely interesting account of why scientific inquiry has become so valued in our culture -- an important source the thought that empirical inquiry is more respectable than philosophical inquiry is a more general attitude that treats the fruits and methods of scientific inquiry as among the most respectable forms of inquiry full stop.

So, for example, this attitude helps to explain the righteous indignation of many liberals (and, indeed, others) towards politicians who seemingly ignore the results of scientific inquiry. Likewise, according to one conventional theory the rise in the esteem of science is so important in our culture that it has "pushed out" or "subtracted away" important religious practices and attitudes and so has led to a change and diminution of religion.

Scholars who work in the history of ideas may be best equipped to explain the rise in the esteem of science over the last centuries, but one philosopher who does very interesting work in this is Charles Taylor. In his A Secular Age, Taylor constructs a fascinating and extremely rich narrative that addresses this and many related changes -- and, notably, he does no while utterly rejecting the standard "subtraction account" according to which rise in the esteem of scientific inquiry inevitably leads to the diminution of religion.