The theory can be put to a certain test by considering its implications with respect to colour.
Ray Lankester, have urged that the word is so firmly asssociated with historical implications of fixity which are now incongruous with its application, that it ought to be discarded from scientific nomenclature.
The function of logic is to exhibit its formal implications and repulsions.
The implications of such a view were first clearly apparent when Hume showed that on the basis of it there seemed to be nothing that we could confidently affirm except the order of our own impressions and ideas.
Now it is just to these implications in the idea of spirit that some of the prominent recent expositions of Idealism seem to have failed to do justice.