ABSTRACT
ALL that we have seen so far suggests that the key problem which larises in the construction of classes is that of co-ordinating extension and intension. In order to tackle this question directly we tried to devise experiments bearing directly on the problem of class-inclusion, i.e. the fundamental extensive relation which subsists as between a subclass (= “some”) and an enveloping class (= “all”), where both are fully determined by a number of intensive relations or qualities.
