I believe it is an established maxim in morals that he who makes an assertion without knowing whether it is true or false, is guilty of falsehood; and the accidental truth of the assertion, does not justify or excuse him.

Lincoln’s statement draws a sharp ethical line between being right and being responsible. He argues that truthfulness is not merely a matter of whether a claim happens to match reality, but whether the speaker has adequate grounds for making it. To assert something while indifferent to its truth is, in his view, a form of lying because it treats accuracy as accidental rather than intended. The remark also implies a civic dimension: public discourse depends on conscientious verification, not lucky guesses. In effect, Lincoln frames moral accountability as tied to epistemic duty—speakers must care whether what they say is true, and must speak in proportion to what they actually know.