In late 2008 or something, Philip Swenson and I were driving to Vegas on a spontaneous poker run, and we were lamenting the fact that Gary Watson was leaving UCR. Philip was a first year grad student at the time, so I "magnanimously" volunteered some information about this awesome workshop on psychopathy that Gary and John Fischer had run the year before ("oh man, you really missed it!"). From there, we started talking about psychopathy and whether it was an exempting condition on responsibility, or perhaps, only a mitigating one. And this conversation eventually led to the theory of degrees of responsibility that we developed in "Reasons-Responsiveness and blah, blah blah..."
Of course, Philip and I certainly aren't the only folks to think about degrees of responsibility. It's something that folks working on criminal responsibility have talked about a good bit. And recently, folks working on moral responsibility (e.g., Dana Nelkin, Manuel "other people can promote his work as well" Vargas, and Michael McKenna and Benjamin Kozuch) have been working on it and related issues as well.
But for all this, I think that what it is we're talking about when we're talking about degrees of responsibility is relatively obscure. In particular, I think there are two (or really, three) conceptually and normatively distinct properties that we could be talking about when we're talking about degrees of responsibility. And so I think it will be incumbent on a plausible theory of degrees of responsibility that it accurately specify which of these properties it refers to, since the conditions under which one of these properties is instantiated might be significantly different than the conditions under which another of these properties is instantiated.