Talcott Parsons : (3)

" The main concern of the study is with the outline of a theoretical system. Its minor variations from writer to writer are not a matter of concern to this analysis. " - Talcott Parsons

" If observed facts of undoubted accuracy will not fit any of the alternatives it leaves open, the system itself is in need of reconstruction. " - Talcott Parsons

" If there are four equations and only three variables, and no one of the equations is derivable from the others by algebraic manipulation then there is another variable missing. " - Talcott Parsons