How would you make a 4 dimensional being believe in its existence?
Lets start with looking backwards at the dimensions since you must understand the lowest D possible.
I was going to start with the 3rd dimension, but I think it would be safe to say that we can all agree that the 4th dimension is time.
Then we have the 3 dimensional beings, us. I don't think that anyone cannot consider us 3 dimensional beings, can you? So our three dimensions would be...