reason vs should

reason

verb
  • To persuade by reasoning or argument. 

  • To support with reasons, as a request. 

  • To arrange and present the reasons for or against; to examine or discuss by arguments; to debate or discuss. 

  • To find by logical process; to explain or justify by reason or argument. 

  • To deduce or come to a conclusion by being rational 

  • To overcome or conquer by adducing reasons. 

  • To perform a process of deduction or of induction, in order to convince or to confute; to argue. 

noun
  • That which causes something: an efficient cause, a proximate cause. 

  • An excuse: a thought or a consideration offered in support of a determination or an opinion; that which is offered or accepted as an explanation. 

  • A premise placed after its conclusion. 

  • A motive for an action or a determination. 

  • Rational thinking (or the capacity for it); the cognitive faculties, collectively, of conception, judgment, deduction and intuition. 

should

verb
  • Used to give advice or opinion that an action is, or would have been, beneficial or desirable. 

  • Will be likely to (become or do something); indicates a degree of possibility or probability that the stated thing will happen or be true in the future. 

  • Indicates that something is expected to have happened or to be the case now. 

  • Used to express a conditional outcome. 

  • With verbs such as 'see' or 'hear', usually in the second person, used to point out something remarkable in either a good or bad way. 

  • To make a statement of what ought to be true, as opposed to reality. 

  • Used to impart a tentative, conjectural or polite nuance. 

  • Used to express what the speaker would do in another person's situation, as a means of giving a suggestion or recommendation. 

  • Simple past tense of shall. 

  • In questions, asks what is correct, proper, desirable, etc. 

  • Used to issue an instruction (traditionally seen as carrying less force of authority than alternatives such as 'shall' or 'must'). 

  • Used to form a variant of the present subjunctive, expressing a state or action that is hypothetical, potential, mandated, etc. 

noun
  • Something that ought to be the case as opposed to already being the case. 

How often have the words reason and should occurred in a corpus of books? (source: Google Ngram Viewer )