  However, there is a counter argument due to D.S. Wilson (1977, 1980), who maintains that weak altruism cannot evolve by individual selection alone; a component of group selection is needed. Wilson's argument stems from the fact that in a mixed (W,N) pair, the non-altruist is fitter than the weak altruist. More generally, within a single group of any size containing weak altruists and non-altruists, the latter will be fitter. So weak altruism can only evolve, Wilson argues, in a multi-group setting—in which the within-group selection in favour of N, is counteracted by between-group selection in favour of W. (On Wilson's view, the evolutionary game described above is a multi-group setting, involving a large number of groups of size two.) Thus weak altruism, like strong altruism, in fact evolves because it is group-advantageous, Wilson argues.