In her 1996 paper on self-knowledge, Victoria McGeer proposes that one of the main reasons a person's claims about her attitudes are likely to be true is this: Once you avow an attitude (whether to yourself or others), you are thereafter committed to living and speaking and reasoning in accord with it (unless you can give some account of why you're not doing so). Since you have considerable self-regulatory control over how you live, speak, and reason; and since all there is to having an attitude is being prone to live, speak, and reason in accord with it, you have the power to make what you say about yourself true. In short, you shape yourself to accord with the attitudes you express. In McGeer's view, self-knowledge has more to do with this sort of self-shaping than it does with any introspective phenomenon of discovering attitudes that already exist.
Now, I'm not sure our claims about our attitudes are as likely to be right as philosophers often assume -- especially our most morally relevant implicit habits of acting and reacting, valuing and disdaining, in the ordinary run of life -- but it seems to me that there's something importantly right in McGeer's view here, especially with respect to love.
Suppose I'm up late with some friends at a bar. They're talking jazz, and I'm left in the dust. More to participate in the conversation and to seem knowledgeable than out of any prior conviction, I say, "I just love Cole Porter ballads." I could as easily said that I love Irving Berlin or Rogers and Hart. About all these composers, I really only know a half-dozen songs, which I've heard occasionally performed by different artists. My friends turn to me and ask what I like about Porter; I say something hopefully not too stupid. Later, when we're driving in my car, they expect to hear Cole Porter. When a movie on Porter comes out, they ask my opinion about it. I oblige them. Let's say, furthermore, that such a pattern of behavior isn't just a show for them. In light of what I said, I find myself more drawn to Porter in the future. This isn't at all preposterous: The psychological literature on cognitive dissonance, for example, suggests that we tend to shape our genuine opinions to match what we have said, if it was said without obvious coercion.
Thus, I have transformed myself into a Cole Porter fan by means of an arbitrary remark. It wasn't true of me before I said it; but now I've made it true. If love is a kind of commitment to value something or pattern of valuing it, I embarked on that commitment and began that pattern by making the remark. Its truth derives not from accurate introspection but from the fact that I work to make myself consistent and understandable to myself and others.
If I say to myself -- or, shall we say, decide? -- in the scoop shop that I love Chunky Monkey ice cream, I am at least as much forming a commitment, establishing a pattern, or creating a policy as a reference point for future deliberation, as I am scouring my mind to discover a pre-existing love. (Of course it's highly relevant that I remember enjoying Chunky Monkey so much last time I had it.) If I tell someone for the first time that I love her, I am not -- I hope -- merely expressing an emotion (emotions pass so quickly!) but embarking on a commitment of a certain sort, making a decision, embracing a habit of valuing her in a certain way. (This is partly why first confessions of love are so frightening.) Though the various phenomena we call "love" differ in many ways, it seems to me they share a self-commissive aspect in their expression that makes them ripe for an analysis along McGeer's lines.
Of course, there's a very different kind of commitment involved in deciding one loves Chunky Monkey than in announcing one's love for another person, and we think very differently about people who back out of these different commitments. But even with respect to the smallest love, we need a certain amount of self-consistency. One cannot ceaselessly and arbitarily flop around in one's loves and values and continue to be a normal reasoner and normal member of a community.
Similar observations hold, in varying degrees, for other attitudes: beliefs, desires, fears, hopes, plans. The introspective views of self-knowledge that dominate philosophy (e.g., Nichols and Stich, Goldman) don't give sufficient attention to this self-shaping aspect.
By the way, I'm tempted to think that this kind of self-knowledge through self-shaping can sometimes find a parallel in other-knowledge through other-shaping: Imagine a mother who announces that her four-year-old son loves baseball and then works to make it true. Or imagine Stalin announcing that his people despise Zinovievites.