However, even supporters of Rawls acknowledge that his work raises many questions. One of the earliest major responses to the book came from his Harvard colleague, philosopher Robert Natick. In Anarchy, State, and Utopia (1974) Nozick offers a libertarian response to Rawls. The assumptions behind A Theory of Justice are essentially redistributive: That is, Rawls puts forward equal distribution of resources as the desirable state and then argues that inequality can be justified only by benefits for the least advantaged. Nozick points out those resources are produced by people and that people have rights to the things they produce. Thus, attempts to improve the condition of the least advantaged through redistribution are unjust because they make some people work involuntarily for others and deprive people of the goods and opportunities they have created through time and effort. Nozick attacks John Rawls's Difference Principle on the ground that the well-off could threaten a lack of social cooperation to the worse-off, just as Rawls implies that the worse-off will be assisted by the well-off for the sake of social cooperation. (JF, 78-83) Nozick asks why the well-off would be obliged, due to their inequality and for the sake of social cooperation, to assist the worse-off and not have the worse-off accept the inequality and benefit the well-off. Nozick argues that natural advantages that the well-off enjoy do not violate anyone's rights and therefore have a right to them, on top of which is the fact that Rawls's own proposal that inequalities be geared toward assisting the worse-off is in it morally