The Burden of Proof

Myself & my relatively uninteresting friend came back to the house we had earlier left in the pursuit of the kind of everyday activities it would bore me to describe, such as, for example, shopping. When we entered the living-room, there was now, unexpectedly, a dining-table & chairs of sturdy & simple design which had not been there two hours earlier.
Who could have brought these in, I wondered aloud.
What do you mean, asked my friend. I was somewhat surprised at his question.
"Exactly what I say. They are here now. They weren't here earlier. So somebody brought them in."
"Excuse me but what we have here is a suite of furniture. I see no need to introduce an unknown element such as someone, of whom there is no sign, bringing it in."
"But that's ridiculous. The very presence of this dining-table & chairs necessitates person or persons unknown having placed these objects here."
"You are complicating the issue. I see no sign of this mysterious person or persons."
"So what's your theory of how they got here? That they simply materialised of their own volition?"
"That is not my concern. You are the one talking of this other element. Yours is the burden of proof. I see no need to justify my position, this being simply the absence of belief in your strange person unknown theory, but to demonstrate my intellectual magnanimity, perhaps there was some kind of bang which set a scientific train of events in motion which produced the furniture we have now before us."
This was the occasion on which I desisted from speaking to my friend for an extended period. I am, after all, not a violent man.