Proving Linear Theory: Key Points Needed

[xylai]

How can we know a theory is linear. That is to say, if we want to prove that a theory is linear, what is the key points or the key parts that we need prove.
Thank you!

 

[olgranpappy]

usually this means that the differential equation(s) that make up the theory are linear differential equations. E.g., the Schrödinger equation.

 

[xylai]

Thank you!