On Bishop George Berkeley's Three Dialogues Between Hylas and Philonous (1713).
While only a goon would deny the real existence of things like tables and chairs, does "real" existence have to mean existence as matter, i.e. as something that could exist in the absence of any mind to think about it? Berkeley says no! Tables and chairs are ideas! But not just my ideas, or yours, as they obviously don't disappear when we leave the room, and certainly trees and the like were around before people. So they're God's ideas! And hey, this chain of reasoning actually provides a proof for God's existence! Sweet!
Wes tries to convince Mark and Dylan that this is actually compelling, well argued, and motivated by deep philosophical concerns that were historically central and still relevant today. By all means, listen to Wes's lengthy and excellent summary before tackling this discussion, and you can also read more about the topic and get the text.