The "Stanford Encyclopedia of Philosophy" and the "New Catholic Encyclopedia" provide two possible replies to the above objections. The first reply is that the mind may influence the "distribution" of energy, without altering its quantity. The second possibility is to deny that the human body is causally closed, as the conservation of energy applies only to closed systems. However, physicalists object that no evidence exists for the causal non-closure of the human body. Robin Collins responds that energy conservation objections misunderstand the role of energy conservation in physics. Well understood scenarios in general relativity violate energy conservation and quantum mechanics provides precedent for causal interactions, or correlation without energy or momentum exchange. However, this does not mean the mind spends energy and, despite that, it still doesn't exclude the supernatural.