"Building on Hume, we see that the fallibility of human reasoning means that a person cannot obtain absolute certainty in any matter save for trivial cases where a statement is true by definition (as in, "all bachelors are unmarried" or "all triangles have three angles"). All rational statements that assert a factual claim about the universe which begin with the statement "I believe that..." are simply shorthand for the statement "based on my knowledge, understanding, and interpretation of the prevailing evidence, I tentatively believe that..." For instance, when one says, "I believe that Lee Harvey Oswald shot John F. Kennedy," said person is not asserting an absolute truth but rather a tentative belief based on an interpretation of the evidence assembled before them. Even though one may set an alarm clock at night, fully believing that the sun will rise the next day, that belief is tentative, tempered by a small but finite degree of doubt, since there is always some infinitesimal measure of possibility that the sun might explode or that that person might die, and so on." https://www.newworldencyclopedia.org/entry/Agnosticism