Here’s my theory. Which is mine. *cough cough*
People work to get rewards and avoid punishments and does so in a way that makes internal sense to them.
That’s my Theory of Everything. It elegantly models and explains all of human behavior, much like E=mc^2 explains (nearly) all of physics. Of course, like E=mc^2, it’s practically useless in application. Think about it – even something only marginally less vague than E=mc^2 – like F=mv – still requires some definitions. What is force? What is mass? What is velocity?
Likewise, most of our problems coming up with theories of human behavior trip up on other people deciding what constitutes reward and punishment. My idea of a reward – say, a new electric SmartCar – might not be yours if you want a new SUV. 77 virgins? Not my cup of tea.
There are a lot of commonalities in what constitutes reward and punishment in any society. That makes it easy – and frequently accurate – to generalize those rewards and punishments to all members of that society. But it is also, obviously now, a logical fallacy to do so.
In one sense, my sociological ToE is deeply unsatisfying. It has a lack of real-world practicality. But it is a deep structure, a framework on which all other theories can conveniently hang. By itself, it doesn’t explain every detail – but it provides a framework that other, more detailed explanations fit into.
When striving for a ToE, that is perhaps the best goal one can strive for.