and (ii) are non-overlapping [i.e. have no extensive component in common].
If the determinate function be that of simple addition [so that,
being the quantities possessed respectively by
and its two extensive components,
], then the kind of quantity will be called 'absolutely' extensive. When an extensive quantity is not absolutely extensive, it will be called 'semi-extensive.'
59.2 It is usual in philosophical discussions to con- fine the term 'extensive quantity' to what is here defined as 'absolutely extensive quantity,' and to ignore entirely the occurrence of semi-extensive quantities. But in physical science semi-extensive quantities are well known. For example, consider a sphere of radius