There has been much discussion of the right to explanation in the EU General\nData Protection Regulation, and its existence, merits, and disadvantages.\nImplementing a right to explanation that opens the black box of algorithmic\ndecision-making faces major legal and technical barriers. Explaining the\nfunctionality of complex algorithmic decision-making systems and their\nrationale in specific cases is a technically challenging problem. Some\nexplanations may offer little meaningful information to data subjects, raising\nquestions around their value. Explanations of automated decisions need not\nhinge on the general public understanding how algorithmic systems function.\nEven though such interpretability is of great importance and should be pursued,\nexplanations can, in principle, be offered without opening the black box.\nLooking at explanations as a means to help a data subject act rather than\nmerely understand, one could gauge the scope and content of explanations\naccording to the specific goal or action they are intended to support. From the\nperspective of individuals affected by automated decision-making, we propose\nthree aims for explanations: (1) to inform and help the individual understand\nwhy a particular decision was reached, (2) to provide grounds to contest the\ndecision if the outcome is undesired, and (3) to understand what would need to\nchange in order to receive a desired result in the future, based on the current\ndecision-making model. We assess how each of these goals finds support in the\nGDPR. We suggest data controllers should offer a particular type of\nexplanation, unconditional counterfactual explanations, to support these three\naims. These counterfactual explanations describe the smallest change to the\nworld that can be made to obtain a desirable outcome, or to arrive at the\nclosest possible world, without needing to explain the internal logic of the\nsystem.\n