The question of  how to tell if a woman is interested in a man is a subtle one indeed. This seems to me to be the more interesting of the questions you suggest. No one can give you a definitive answer except this woman, of course, but still one can say several things.

First, the issue of mixed signals. You were not specific, so I will have to assume you are a reasonably astute observer of human nature and are not simply ignoring obvious nos out of misguided hope. In this case, it is useful to remember that desire is not homogeneous. Even among two people madly infatuated, the quality of attraction varies from moment to moment. It lulls; it surges. If you cook at all seriously you will have noticed the wide variety of ways in which water boils; in any case metaphors of this sort abound. And if you cook with a gas stove -- the moment you stop applying heat, the boiling stops. Everyone is hypersensitive to certain things. You mention your love of analytic philosophy, and she melts. You slurp your soup, and she goes cold. Of course she may not be so silly -- it could be your misinterpretation of Wittgenstein.

Once the relationship has progressed a bit beyond the surface, its flames are not so much in danger. But the very beginnings of flirtation can be skittish. Wide swaths of character are read into the smallest gestures -- we are in the realm of great hopes, ruthless judgments, wild exaggerations. You are probably the same way; after all at this point you barely know her. Nonetheless the human ego, while jealously guarding its own right to be ambivalent, often demands total devotion from the other...

The point for you is that, provided once again that one is observant enough to catch the obvious signals, the right assumption is very rarely that the other person -- male or female -- has a strong idea of where the relationship is headed. There is often at the beginning quite a period of limbo. It may not be in your best interests to immediately force the resolution of the issue. I would suggest you move slowly in the direction of more serious involvement.  Spend time one on one -- you have an obvious excuse in editing each other's creative work. Of course, at the same time, if you hope to date it is important not to let a pattern of asexual friendship set in. There are many small ways to encourage (and not to avoid) touch, e.g. as one walks through the dangerous world with cars whizzing this way and that, and the response here -- even to a hand on her arm -- will tell you a lot. If after several weeks of more intense interaction you don't feel the tide has turned or the signals are clear, you may want to call in your most observant friends for an objective opinion.

(Of course, there's also talking to her.)

I agree with some of the points in the previous post but I would characterize it completely differently, to wit: It is not such a terrible thing to live with uncertainty. While I appreciate the quality of intensity she is perhaps trying to describe, I disagree with Catherine's emphasis on hypersensitivity. People are not, in my experience, quite so fickle. They usually do not spend the better part of a dinner swinging violently between extreme states.
They are, however, often profoundly uncertain, both about what they want and what they feel, and consequently it is empirically true that many very important decisions -- especially decisions about relationships -- are consequences of inertia, impulse, and/or misunderstanding.

The point, Rick (which, I should add, has nothing to do with your gender) is that at some critical juncture between being a child and becoming an adult (see also an interesting post on this topic), one ceases to experience oneself purely as a passive observer of the world and begins to take an active place in shaping it. In case it's not obvious, I'll say very clearly that this certainly does not mean you begin to see other human beings as instruments of your will. But it does mean that you understand that, in a subtle but unmistakeable way, you are a participant in the process of living. The effect is that the world becomes somewhat less flat. Your range of action extends beyond hopeful waiting. This has consequences for life, for fulfilling your potential, for pushing yourself to do great work, for friendships, and of course for relationships.

What does this mean for your particular situation? You haven't given many details. However, if you really think that you and X would be wonderful together, it makes sense to make your argument directly to her. How, precisely, to do this -- and how explicitly -- depends very much on the characters involved. The simplest advice is to show her that you appreciate her and are sensitive to all her amazing qualities -- not limited to of course, but certainly not excluding, the physical -- and to create as many opportunities as possible for her to see the same things about you. And not to be afraid to use the word "relationship." As for how to speak, experience helps, but a good rule of thumb is to be sincere and, when unsure, to keep things light, which is not the same as not serious. Giving true compliments sincerely and well is an art, and requires practice. Finally, you of course need to be sensitive to her response.

But also, enjoy yourselves. There is something interesting, at times even exhilarating, about these moments where one sees that many different things are possible. Who knows where this will go? It's not a question of control; there may be many factors besides you. Nonetheless your actions have an effect. Act wisely, and well!

Hi Rick,
You ask whether the girl you have been spending a little time with is interested.  I think your question is essentially flawed.  It assumes that she knows whether or not she is interested.  That is not how it works.

She is meanwhile getting to know you, and you have to find a way to push things to the brink of a relationship.  If you are too slow about it, she will decide that you are boring.  Not that you were boring in any other way!  So get on it.

Probably this is disastrous advice, so take it at your own risk.