Socialists argue that collectivism, which implies cooperation with others rather than competitive individual self-striving, is both morally and economically superior to individualism. This argument also relates to the socialist critique of capitalism, as an example of economic individualism. Collectivism is seen as morally superior because it leads to cooperation and prevents the conflict and aggression caused by individual self-striving. It has a positive and unifying effect on society and has both moral and economic benefits. This is linked to the socialist interpretation of human nature that sees humans as naturally social, altruistic beings, so collectivism is a natural development. It is economically superior because it prevents unnecessary and wasteful competition and in theory results in greater productivity. In the nineteenth and twentieth centuries, collectivism was mostly associated with the state being the collectivist body, as an alternative to the private ownership associated with capitalism. However, collectivism has been interpreted in many different ways by different types of socialists. For fundamentalist socialists/ communists in the twentieth century, such as Fidel Castro, collectivism was interpreted as state planning and the abolition of private property. This involved the nationalisation of all the means of production, leading to total state control of the organisation of the economy. In contrast, social democrats would see collectivism as exemplified by the welfare state, a system where all contribute via progressive taxation and all benefit, with no opt-outs. Another form of collectivism which is not associated with state power is the trade union movement. Trade unions are based on the collectivist idea that workers coming together to form democratic organisations will achieve a better outcome for all. The cooperative movement is also an interesting example of collectivism. Cooperatives can be worker owned or consumer owned. The Co-operative Group in the UK is a successful example.