A man wants to know is the past real or just a concept? He says he can clearly see that the future is only an idea, but what about the past? To what extent is the past real?
Rupert says we can only find out by exploring our experience. We actually have to go there, touch the past, hold it in our hands and investigate it. Can you actually go there?
I'm not suggesting there isn't some reality to time or the past or memory. There is something real about our experience of time, and that is the eternal now. But our mind imposes its own limitations on that reality and makes it appear in a way that is consistent with that.
So, we cannot think about this satisfactorily. You just cannot see white snow through orange tinted glasses. We just cannot perceive the nature of reality through the limitations of a finite mind.