Speaker B
You presumably know what date you were born. Well, you certainly trust the veracity of your birth date. Well, what justifies that belief? It's possible that when you were very young, when you started school perhaps, your parents told you when you were born. But do you trust your parents? And I don't. Now, if I had doubts about my parents, which I don't, but if I did, I could check the newspaper of that day in the city where I was born, or my birth certificate, and see what it says. See if it matches what they told me. Ah, but the point is that even checking the birth certificate, one is still trusting other people, because that birth certificate was made by other people, just like the newspapers that go back far enough, that also was written by people.