"We may regard the present state of the universe as the effect of its past and the cause of its future. An intellect which at a certain moment would know all forces that set nature in motion, and all positions of all items of which nature is composed, if this intellect were also vast enough to submit these data to analysis, it would embrace in a single formula the movements of the greatest bodies of the universe and those of the tiniest atom; for such an intellect nothing would be uncertain and the future just like the past would be present before its eyes." -- Laplace
My understanding is that Laplace's demon was primarily intended as a heuristic for understanding microphysical determinism. But there is a serious question (noted by or implicit in the work of a number of philosophers of science, e.g., Sober, Loewer, Albert) as to whether, in fact, "nothing" about the physical universe would escape the demon's knowledge. There is some ambiguity in what is meant by "submit these data to analysis," but intuitively it seems that the demon's abilities would only allow him to know all of the facts describable in microphysical terms. There is a real question then about whether this would amount to knowledge of all of the facts, including about mereologically composite objects, let alone about minds.
Would we need to add to the demon's capacities, then, some sort of additional "translation manual" to tell him which macro-states are being realized by the micro-physical states? And would this amount to a problem for a reductionist picture of the world? Maybe, maybe not.