The third floor does exist

I must admit, this blog post title isn't as interesting as my last one. But nonetheless it relates to what I did in IB Philosophy today. So, let's get started. How can you prove something exists? What is the basis of its existence? Do I exist? How do I know that I am real, and not a character from a book?
I've never really wondered about mankind's existence until today. Recently, I have been very intrigued with reading Sophie's World. The book not only provides a view into the history of philosophy, but the book also uses philosophy to address philosophical questions such as the difference between the real world and the imaginary world.

Imagine you were given a task. This task was to prove that the third floor of your school does indeed exist. How would you address the question? One of the first things you might think of is that the third floor exists because it is part of the school and you walk through its hallways everyday. Well, that is true. But there are other ways the you could prove the third floor exists. You could say that if you asked someone who was on the third floor "what floor are you on?" they would reply with "third floor." Each floor in our school is distinguished by a sign that reads what floor they are on. Logically, if the sign reads "3rd Floor" than we are obviously on that floor.

There are logical fallacies to my thinking on whether or not the third floor actually exists. It could just be that all the floors in the school are someway connected by the stairs. This allows the school floors to actually be just one huge floor (if that makes sense?).