The law of flexible problem solving is the principle that flexible problem solving finds ways to overcome problems. It means that it is not possible to have a flexible problem solving ability with fixed limits. If there is any flexible problem solving ability around, it can find ways to identify the problem and solve it. For there to be any fixed limits at all, flexible problem solving must be absolutely absent. This implies that evolution happens by removing obstacles rather than natural selection. As shown in moderating the free will debate and brain, justification and pressure to justify constitutes obstacles that must be removed, see evolutionary development in new niches and advice of ways to stop justifying. It also explains how science can exist at all.