Nicely recapped by R. L. Anderson:
… let us return to the expressivist account of successful action, which is nicely captured in Pippin’s paradigm examples of artistic intention. Suppose my intention is to write a good poem. Unfortunately, I am no poet, so my results are execrable. The power and interest of the expressivist identification of intention with action arise just here. Precisely because the character of my intention can be defined by the actual outcome of my activity, I run afoul of the lightning-flash identity argument when I insist that this is not the poem I intended to write. My actual poem does express my intention (where that is defined in terms of the process of action), so it is bad faith to disown it. What my discontent seeks is not fairly described as the good poem I intended to write; at best, what it wants is to have had a different intention altogether, one that could have produced a different, better, poem. The availability of this analysis depends on the thought animating the first horn of the dilemma—that the content of my intention is ineluctably defined in terms of the proper interpretation of the resulting action.
Right down to the tendentious "proper" in the last sentence. I think it's worth pointing out how weird the intention to write a good poem is, too, but that's probably inessential. (Obviously, I can only speak to the production of doggerel and parodies, but I don't think I've ever sat down to write anything with the goal of just writing a good X, and it seems like a bizarre way to take artistic intentions generally.)
Nehamas also makes use of this kind of creative example, if I remember correctly, and also uses specifically artistic creation (I believe I've heard him use specifically poetry, for that matter). It's a nice example for polemical purposes but a bad one, I think, for philosophical. It's good for polemical purposes because the bad poet who insists that he didn't mean to write this poem can't, if challenged with the question what poem he did mean to write, produce a different, better one and say: "well I wanted to write this one, see." (Of course, he can say "I intended to write a good poem, not this ungainly mess", or "I wanted to write a poem that would …"—and it's never really been clear to me why that isn't enough. We could call it the Travis Bickle Theory of Intention: "I don't see any other poems around here.") If he could have done that, he would have written that one. It obviously isn't a question of his reproducing an already existing poem, after all, and the only poem on the scene is the bad one actually produced.
That's not essential to the example, though; the example ought to work with any instance of incompetence. It ought to work equally well if I mess up the roasting of a chicken or the construction of a birdhouse, which are (or at least can be) exercises in copying models or following procedures. If the bird is burnt black, or the birdhouse a Escherian puzzle, and I say: "I didn't mean to do that", though, I can say what I intended: I point to the picture in my illustrated cookbook, or woodworking book, and say, "I wanted to make that". To deny that that is a sound expression of one's intention is bats; it would be like insisting that in order really to refer to something we have always to engage in the "singular stroke of eloquence" that Dr. Slothrop attempts in Tristram Shandy, whereby instead of giving the name of a thing one just produces the thing itself. "I wanted to build a [here I produce from my mantle a birdhouse]"—and even here, I could produce another birdhouse, not built by me, since I'm not trying to build an original birdhouse anyway.
To say that the shambles of a birdhouse I actually build "expresses my intention (where that is defined in terms of the processes of action)" begs the question, since clearly the upshot of the processes of action I engaged in—assuming I haven't been interfered with—can't be other than the upshot of those very processes. What might be meant in this case by saying my discontent with it really means that I wish to have intended something else? Does that mean, to have intended to produce a different birdhouse than the one exampled in the pages of my book? Not that. Perhaps it means that I wish to have had different sub-intentions in carrying out the construction project—e.g. that I should have intended to drive the nail in straight rather than incompetently? But that obviously gets us nowhere (I did intend to drive the nail in straight, I'll insist). I am not sure what other reasonable interpretations there are, here, or why we shouldn't just say that while I intended to do one thing, I was incompetent, and thus ended up actually doing something else. On Pippin's account it seems as if I always only execute my actual intentions just fine, and incompetence is isolated to my initial identification of what I'm about in the first place.
The actual birdhouse I end up building can still be plausibly claimed to "express my intention" in the following sense: I intended to build a birdhouse like the one in the book, acted on the intention, and produced this thing, which is very unlike it. And one could sensibly say that, therefore, it's bad faith for me to disown the birdhouse. It's not what I wanted but it is what I did (and if I want to get better at woodworking it would be advisable for me to try to understand what I did wrong). But that's consistent with denying that this thing is what I intended to produce, on any sane use of the concept of intention.