 Grammatical reasoning, then, finds itself wedged between physical and logical reasoning. This can be seen in the analysis of the expression, est dies. Why one term and not two? What is the function of dies? In an analysis of motion there are two terms. But in reason, one can see that the one term has two functions that are necessarily present in every assertion. And whereas Logic requires that the subject be different from the predicate, Grammar as a positive science depends on the intellect and will. 