 Suppose we are presented with a set of fancy mechanical devices and are asked to select the five best tin openers from these. No detailed study of the internal properties of each will allow us to accomplish that task. We have to analyse each in relation to a tin and try to determine the way in which it might open it. Only then would we be able to conclude which particular properties of the mechanisms are correlated with good tin-opening abilities. In the same way we can only regard an internal quality of a way of accessing the world as a characteristic of an epistemic instrument once we have assessed it in relation to the objects cognized. Only then can we conclude that this particular property really leads us to the knowledge of the nature of the object, rather than doing something else. But in this case the establishment of the epistemic instruments can no longer be regarded as self-establishment since it incorporates reference to other objects (namely the objects known) at an essential place.