Final answer:
Philosophers argue that truth is not relative and there is only one truth value for statements and propositions. Just because someone can't determine the truth of a statement doesn't mean there is no truth.
Step-by-step explanation:
Philosophers who argue that knowledge of the external world is impossible do so based on the idea that one can never be certain of the truth of one's external world beliefs. But what does it mean to claim that a belief is true? People are sometimes tempted to believe that truth is relative. A person may say things like "Well, that's just their truth" as if something can be true for one person and not for others. Yet for statements and propositions, there is only one truth value. One person can believe that Earth is flat while another can believe is it round, but only one of them is right. People do not each personally get to decide whether a statement is true. Furthermore, just because one has no way of determining whether a statement is true or false does not mean that there is no truth to the matter. For example, you probably don't quite know how to go about determining the exact number of blades of grass on the White House lawn, but this does not mean that there is no true answer to the question. It is true that there is a specific number of blades of grass at this moment, even if you cannot know what that number is.