The Universality of Laws in Space and Time

Part of our folklore is that genuine laws of nature must be universal in space and time. The purpose of this note is to explicate and compare various senses of this requirement. I am not concerned to argue here that the requirement, in any one of its explicated forms, should or should not be adopted. If it is hard to state straight out exactly what is demanded by universality in space and time, Michael Tooley has provided an example of a hypothetical law which fails the requirement in a significant sense: All fruit in Smith’s garden at any time are apples. When one attempts to take an orange into the garden, it turns into an elephant. Bananas so treated become apples as they cross the boundary, while pears are resisted by a force that cannot be overcome.