Dialectics (logic) is the "head" of the Trivum -- if  Grammar is the "heart" and Rhetoric where they converge.  Instead of describing the world as it is – the job of grammar – it points towards what could be if we alter the underlying structures.  If grammar refers to the reality of “nature,” then dialectics opens the door for the potentially “unnatural.”  As a result, dialectics is often associated with “progress” or even radical change (as in the Marxian use of the term).  McLuhan's PhD thesis, titled “The Classical Trivium,” is an account of the tension between Grammar and Dialectics – one which cannot be resolved, although the balance shifts.  The Print paradigm drove Logic to overpower Analogy.  Today's Digital paradigm heightens the urgency of this grammar/dialectics tension, since humanity's future aligns with the outcome.