It literally means, ‘whatever you see and whatever you do not see bear testimony to the veracity of this discourse’ that is, whatever knowledge was at the command of humanity at the time the Quran was revealed and whatever was going to come within its reach thereafter, both go to prove the truth of the messenger’s utterances. Neither the present available knowledge contradicts the Quran being the Truth, nor will future knowledge be able to do so. In spite of this, those who do not accept it simply prove that they are not serious about Truth and Untruth.