Laws of nature (or scientific laws) are central to the sciences, especially to fundamental physics. They provide the explanatory backbone of the sciences by grounding explanations, causal relations, predictions and counterfactuals. They are intimately related to natures of time, space, and objective probability. While it is the task of scientists to discover what laws there are, it is the task of philosophers to provide accounts of what laws are, i.e. what makes a generalization or equation express a law?