In fact, the notion of value implies a critical reversal. On the one hand, values appear or are given as principles: and evaluation presupposes values on the basis of which phenomena are appraised. But, on the other hand and more profoundly, it is values which presuppose evaluations, "perspectives of appraisal", from which their own value is derived. The problem of critique is that of the value of values, of the evaluation from which their value arises, thus the problem of their creation . Evaluation is defined as the differential element of corresponding values, an element which is both critical and creative. Evaluations, in essence, are not values but ways of being, modes of existence of those who judge and evaluate, serving as principles for the values on the basis of which they judge.
[…] This is the crucial point; high and low,noble and base, are not values but represent the differential element from which the value of values themselves derives.
Deleuze, Nietzsche and Philosophy, p.1-2