Many years ago, the father of management - Peter Drucker - wrote about the theory of business and it is a helpful concept for marketers to understand.
He asks these types of questions:
What are the assumptions of the business environment
What are the assumptions of your companies mission and what it defines as meaningful results?
How are these assumptions in line with your customers - how do they integrate?
The question now is: What is your theory of marketing? Or the theory of the advertisement campaign that you just made?
Lots of theories are just built around of a string of assumptions.
What assumptions are you making right now about your marketing?