A decent summary of Drescher's ideas is his presentation at the 2009 Singularity Summit, here. For some reason I seem to have a transcript of most of it already made, copy + pasted below. (LW tells me that it is too long to go in one comment, so I'll put it in two.)

My talk this afternoon is about choice machines: machines such as ourselves that make choices in some reasonable sense of the word. The very notion of mechanical choice strikes many people as a contradiction in terms, and exploring that contradiction and its resolution is central to this talk. As a point of departure, I'll argue that even in a deterministic universe, there's room for choices to occur: we don't need to invoke some sort of free will that makes an exception to the determinism, no do we even need randomness, although a little randomness doesn't hurt. I'm going to argue that regardless of whether our universe is fully deterministic, it's at least deterministic enough that the compatibility of choice and full deterministic has some important ramifications that do apply to our universe. I'll argue that if we carry the compatibility of choice and determinism to its logical conclusions, we obtain some progressively weird corollaries: namely, that it sometimes makes sense to act for the sake of things that our actions cannot change and cannot cause, and that that might even suggest a way to derive an essentially ethical prescription: an explanation for why we sometimes help others even if doing so causes net harm to our own interests.

[1:15]

An important caveat in all this, just to manage expectations a bit, is that the arguments I'll be presenting will be merely intuitive- or counter-intuitive, as the case may be- and not grounded in a precise and formal theory. Instead, I'm going to run some intuition pumps, as Daniel Dennett calls them, to try to persuade you what answers a successful theory would plausibly provide in a few key test cases.

[1:40]

Perhaps the clearest way to illustrate the compatibility of choice and determinism is to construct or at least imagine a virtual world, which superficially resembles our own environment and which embodies intelligent or somewhat intelligent agents. As a computer program, this virtual world is quintessentially determinist: the program specifies the virtual world's initial conditions, and specifies how to calculate everything that happens next. So given the program itself, there are no degrees of freedom about what will happen in the virtual world. Things do change in the world from moment to moment, of course, but no event ever changes from what was determined at the outset. In effect, all events just sit, statically, in spacetime. Still, it makes sense for agents in the world to contemplate what would be the case were they to take some action or another, and it makes sense for them to select an action accordingly.

[2:35]

[image of virtual world]

For instance, an agent in the illustrated situation here might reason that, were it move to its right, which is our left, then the agent would obtain some tasty fruit. But, instead, if it moves to its left, it falls off a cliff. Accordingly, if its preferences scheme assigns positive utility to the fruit, and negative utility to falling off the cliff, that means the agent moves to its right and not to its left. And that process, I would submit, is what we more or less do ourselves when we engage in what we think of as making choices for the sake of our goals.

[3:08]

The process, the computational process of selecting an action according to the desirability of what would be the case were the action taken, turns to be what our choice process consists of. So, from this perspective, choice is a particular kind of computation. The objection that choice isn't really occurring because the outcome was already determined is just as much a non-sequitur as suggesting that any other computation, for example, adding up a list of numbers, isn't really occurring just because the outcome was predetermined.

[3:41]

So, the choice process takes place, and we consider that the agents has a choice about the action that the choice selects and has a choice about the associated outcomes, meaning that those outcomes occur as a consequence of the choice process. So, clearly an agent that executes a choice process and that correctly anticipates what would be the case if various contemplated actions were taken will better achieve its goals than one that, say, just acts at random or one that takes a fatalist stance, that there's no point in doing anything in particular since nothing can change from what it's already determined to be. So, if we were designing intelligent agents and wanted them to achieve their goals, we would design them to engage in a choice process. Or, if the virtual world were immense enough to support natural selection and the evolution of sufficiently intelligent creatures, then those evolved creatures could be expected to execute a choice process because of the benefits conferred.

[4:38]

So the inalterability of everything that will ever happen does not imply the futility of acting for the sake of what is desired. The key to the choice relation is the “would be-if” relation, also known as the subjunctive or counterfactual relation. Counterfactual because it entertains a hypothetical antecedent about taking a certain action, that is possibly contrary to fact- as in the case of moving to the agent's left in this example. Even thought the moving left action does not in fact occur, the agent does usefully reason about what would the case if that action were taken, and indeed it's that very reasoning that ensures that the action does not in fact occur.

[5:21]

There are various technical proposals for how to formally specific a “would be-if”relation- David Lewis has a classic formulation, Judea Pearl has a more recent one- but they're not necessarily the appropriate version of “would be-if” to use for purposes of making choices, for purposes of selecting an action based on the desirability of what would then be the case. And, although I won't be presenting a formal theory, the essence of this talk is to investigate some properties of “would be-if,” the counterfactual relation that's appropriate to use for making choices.

[5:57]

In particular, I want to address next the possibility that, in a sufficiently deterministic universe, you have a choice about some things that your action cannot cause. Here's an example: assume or imagine that the universe is deterministic, with only one possible history following from any given state of the universe at a given moment. And let me define a predicate P that gets applied to the total state of the universe at some moment. The predicate P is defined to be true of a universe state just in case the laws of physics applied to that total state specify that a billion years after that state, my right hand is raised. Otherwise, the predicate P is false of that state.

[image of predicate P]

[6:44]

Now, suppose I decide, just on a whim, that I would like that state of the universe a billion years ago to have been such that the predicate P was true of that past state. I need only raise my right hand now, and, lo and behold, it was so. If, instead, I want the predicate to have been false, then I lower my hand and the predicate was false. Of course, I haven't changed what the past state of the universe is or was; the past is what it is, and can never be changed. There is merely a particular abstract relation, a “would be-if” relation, between my action and the particular past state that is the subject of my whimsical goal. I cannot reasonably take the action and not expect that the past state will be in correspondence.

[7:39]

So, I can't change the past, nor does my action have any causal influence over the past- at least, not in the way we normally and usefully conceive of causality, where causes are temporally prior to effects, and where we can think of causal relations as essentially specifying how the universe computes its subsequent states from its previous states. Nonetheless, I have exactly as much choice about the past value of the predicate I have defined as I have, despite its inalterability, as I have about whether to raise my hand now, despite the inalterability of that too, in a deterministic universe. And if I were to believe otherwise, and were to refrain from raising my hand merely because I can't change the past even though I do have a whimsical preference about the past value of the specified predicate, then, as always with fatalist resignation, I'd be needlessly forfeiting an opportunity to have my goals fulfilled.

[8:41]

If we accept the conclusion that we sometimes have a choice about what you cannot change or even cause, or at least tentatively accept it in order to explore its ramifications, then we can go on now to examine a well-known science fiction scenario called Newcomb's Problem. In Newcomb's Problem, a mischevious benefactor presents you with two boxes: there is a small, transparent box, containing a thousand dollars, which you can see; and there is a larger, opaque box, which you are truthfully told contains either a million dollars or nothing at all. You can't see which; the box is opaque, and you are not allowed to examine it. But you are truthfully assured that the box has been sealed, and that its contents will not change from whatever it already is.

[9:27]

You are now offered a very odd choice: you can take either the opaque box alone, or take both boxes, and you get to keep the contents of whatever you take. That sure sounds like a no brainer:if we assume that maximizing your expected payoff in this particular encounter is the sole relevant goal, then regardless of what's in the opaque box, there's no benefit to foregoing the additional thousand dollars.