For human ethics, it can convincingly be argued that justice is a central cornerstone and basis. Here, it is suggested that this can, to some extent, similarly be applied to robots. The article makes the argument that Rawls' veil of ignorance in his conception of justice as fairness can effectively be replaced by a much more natural condition of prudent egoism in a finite world. Observing ones' own important interests in an encompassing context paves the way for a guideline for the conduct, which is binding for humans, robots and each and every pragmatic agent with a minimum level of rationality. These arguments do not see humans (forever) in any privileged position: any agent, single human, state, alien or artificial with a certain minimum of general cognitive (and effective) capabilities is bound by a universal negative imperative. This entails that precautious procedures are preferable, and some general prudently constrained flexibility is required for self-consistency and survival.