Although the twentieth century saw a transition to a less goal-directed model of progress, efforts were still made to defend the older vision in which humanity was the predetermined end of evolution and a particular social order the goal of social progress. Christian thinkers still tended to think of evolution as a process driven by cooperation rather than struggle, with humanity and a spiritually mature society as the goals. Even within a Darwinian framework, it has been argued that evolution is subject to constraints that leave something like humanity as the only possible end-point. From the opposite ideological position, Soviet Marxism preserved the image of a sequence of developmental stages leading to the future utopia. With the collapse of the Soviet Union there were suggestions that free-enterprise capitalism is the final end-point of social evolution.