 Now let S be the sentence “There will be a sea battle tomorrow”. If S is true today, it is correct to infer that a sea battle will occur tomorrow. That is, even though the truth of the sentence does not explain the occurrence of the battle, the fact that it is true licenses the inference to the occurrence of the event. Ascending to the purely formal mode (see section 4 of the entry on  Rudolf Carnap),  we can make the point by explicitly limiting inference relations to ones that hold among sentences or other bearers of truth values. It is perfectly proper to infer from the truth of S today that some other sentence is true tomorrow, such as “there is a sea battle today”. Since “there is a sea battle today” is true tomorrow if and only if there is a sea battle tomorrow, then we can infer from the fact that S is true today that it is true that a sea battle will occur tomorrow.