What does this Shakespeare qoute mean???

Hamlet is telling Ophelia not to doubt that he loves her, in the strongest terms this tormented youth can summon up --saying that even if she questions what was generally taken to be true in their time, about some of the most powerful forces in the universe, that the stars are made of fire, and that the sun moves, and if she goes beyond that to question that there is even such a thing as truth, still she should never doubt Hamlet's love for her -- quite ironic, as things turn out (even though he ends the letter to Ophelia with "but that I love thee best, O most best, believe it. Adieu.")