 As stated above, Berlin held both that values are human creations, and that they are ‘objective’. The foundation for this latter claim is unclear in Berlin’s work. The claim that values are objective in being founded on (or expressions of) and limited by certain realities of human nature would seem to provide a defence against relativism, in holding that there is an underlying, shared human nature which makes at least some values non-relative. The argument that values are objective simply because they are pursued by human beings may seem to allow for relativism, if it makes the validity of values dependent on nothing but human preferences, and allows any values actually pursued by human beings (and, therefore, any practices adopted in pursuing those values) to claim  validity.[20]  But this is a reductio ad absurdum, to be deflected by adding two further considerations: how widespread aspirant universal values are; and whether they can be justified in terms of some rationally defensible conception of human welfare.