Which method did Italian Renaissance artists use to give their flat paintings a sense of depth?

Nthe documentary, michael tilson thomas suggests beethoven's overall message in this symphony by stating, "things happen to us in life we can never get over, but it's ok to know that, recognize that and by confessing that easily and generously we perhaps become the biggest possible we can be."

What is the style of this painting?

Why did emerson most likely include the quotation from john brown speech