A range of modal categories concerning reality as it exists assuming that the laws of nature could have been different. The range includes metaphysical contingence, possibility (non-impossibility), necessity, and impossibility. Metaphysical possibility can be described as the status of a statement or series of statements considering all possible worlds—A statement is metaphysically contingent if it's true in some possible worlds and false in others, possible if is true in some possible worlds, metaphysically necessary if it is true in all possible worlds, and metaphysically impossible if it's false in all possible worlds. For example, some philosophers argue that “water is H2O” is a metaphysically necessary statement. Assuming they are right, if we found a world with something 42 exactly like water (tastes the same, boils at the same temperature, and nourishes the body) but it is made of some other chemical, then it would not really be water.