 In many ways primitive active force plays the role of the concept of the subject in the logical version of the PSR. Just as on the logical version the PSR that a is F is explained by the fact that the concept of F-ness is in the concept of a, so too on the metaphysical version of the PSR fact that a is F is explained by the primitive active force of a that determines it to be F. Whereas commentators such as Couturat and Russell emphasize the logical notion of a sufficient reason to the detriment of the metaphysical notion, other commentators see the logical and the metaphysical as two equally fundamental presentations of the same datum (see Frankel 1994).