Meaning

• A cause:

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

  "Mankind should develop reason above all other virtues."

• Something reasonable, in accordance with thought; justice.

• Ratio; proportion.

Meaning

• To deduce or come to a conclusion by being rational

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

• To converse; to compare opinions.

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

  "I reasoned the matter with my friend."

• To support with reasons, as a request.

• To persuade by reasoning or argument.

  "to reason one into a belief; to reason one out of his plan"

• (with down) To overcome or conquer by adducing reasons.

  "to reason down a passion"

• (usually with out) To find by logical process; to explain or justify by reason or argument.

  "to reason out the causes of the librations of the moon"