 Finally, and more fundamentally, even if donations motivated by altruism or solidarity were morally preferable to more self-interested ones (donations motivated purely by the desire for money, for example) it would not necessarily follow that the latter are wrong or should be prohibited. For, it may just be that the former are supererogatory: that while paid donation is merely permissible, unpaid donation is an act of generosity or solidarity that goes beyond what is morally permitted or required (Wilkinson &amp; Garrard 1996).