Franklin uses irony to question how objectively people use reason. Calling humans “reasonable creatures” sounds complimentary, but he immediately undercuts the phrase by suggesting that reasoning can be used to justify whatever a person already wants to do. Instead of allowing evidence and principles to shape a decision, people may begin with a preferred conclusion and then construct arguments in its favour.

The remark does not dismiss reason itself. Its target is rationalisation: the tendency to present desires, habits or impulses as though they were the result of impartial judgement. Franklin’s broader point is that being capable of reasoning does not guarantee that reasoning will be used honestly or critically. Sound judgement therefore requires some awareness of personal motives and a willingness to test whether the reasons offered would remain convincing if the preferred outcome were different.