Reason

``Reason What It Is
  

When a man Reasoneth, hee does nothing els but conceive a summe totall,  from Addition of parcels; or conceive a Remainder, from Substraction of  one summe from another: which (if it be done by Words,) is conceiving of  the consequence of the names of all the parts, to the name of the whole;  or from the names of the whole and one part, to the name of the other  part. And though in some things, (as in numbers,) besides Adding and  Substracting, men name other operations, as Multiplying and Dividing;  yet they are the same; for Multiplication, is but Addition together of  things equall; and Division, but Substracting of one thing, as often as  we can. These operations are not incident to Numbers onely, but to  all manner of things that can be added together, and taken one out of  another. For as Arithmeticians teach to adde and substract in Numbers;  so the Geometricians teach the same in Lines, Figures (solid and  superficiall,) Angles, Proportions, Times, degrees of Swiftnesse, Force,  Power, and the like; The Logicians teach the same in Consequences  Of Words; adding together Two Names, to make an Affirmation; and Two Affirmations, to make a syllogisme; and Many syllogismes to make a Demonstration; and from the Summe, or Conclusion of a syllogisme, they  substract one Proposition, to finde the other. Writers of Politiques,  adde together Pactions, to find mens Duties; and Lawyers, Lawes and  Facts, to find what is Right and Wrong in the actions of private men.  In summe, in what matter soever there is place for Addition and  Substraction, there also is place for Reason; and where these have no  place, there Reason has nothing at all to do. ''

Leviathan