A blow on one’s head cannot possibly be the cause of one’s consciousness of pain; for there can be a world in which there is a blow, say a moderately strong blow, on one’s head – the head of a perfectly normal, living human being – but there is absolutely no consciousness of pain. A can be considered to be the cause of B if and only if A is (logically) necessarily followed by B; the way, for example, the exclusive act of removing one apple from a basket of two apples would necessarily result into the basket containing only one apple, in any possible world, with any possible logical or physical laws. It can be said in this case that the result of the basket of two apples now containing only one apple is caused by the (exclusive) act of removing one apple from the basket. In the case of consciousness, however, it is not (logically) necessary for B (i.e. consciousness) to follow A (i.e. any bodily, spatial process that is normally and wrongly considered the cause of B); for B is (logically) absolutely distinct from A. A can exist without B and B without A.