 Logic Violators: another definition has it that impossible worlds are worlds where the laws of logic fail. This depends on what we take the laws of logic to be. Given some logic L, an impossible world with respect to the L-laws is one in which some of those laws fail to hold (see e.g. Priest 2001, Chapter 9). An impossible world in this second sense will be an impossible world in the first sense, given that logical necessity is unrestricted. But not vice versa. Suppose it’s metaphysically necessary that the Mona Lisa (if it exists) was painted by da Vinci. Then a world in which the Mona Lisa was painted by Neil Buchanan on Art Attack is an impossible world in the first sense but not in the second, for it does not violate any logical law.