Discretion is pervasive in our legal system, and yet we scarcely know what it is. Ronald Dworkin, for example, has compared discretion to the hole in the doughnut. Dworkin\u27s metaphor is unsettling because it so precisely captures our instinctive sense of discretion as dead analytic space. Discretion most often appears to us as merely the negative reflection of the law. It subsists in the interstices of the law. Where the law ends, Kenneth Davis writes, discretion begins. It is as if law and discretion were binary opposites, as if the presence of one signaled the absence of the other. We can have law or discretion, but not both. And this is because, as Herbert Packer put it, The basic trouble with discretion is simply that it is la...