Maybe you wonder why I came up with a new element like Trial&Error. It is not an argument I have invented for the sake of arguments. It's just based on observations during problem solving. Maybe I can convince you to take it as an element in its own right. The following diagram shows a mate which you can solve by trial&error alone. No subtle idea's to be found, no logical reasoning, no pattern recognition of any importance, just try and reject a whole bunch of lines.
Black to move and mate.
You can find the solution here.
The only thing that is needed is precision and stamina.
This problem shows that T&E is an element in its own right. This means that it can and probably should be trained by a separate method. I asociated it with Troyis. You must be able to move the pieces in your head at lightning speed in order to cover all the possible lines. That is a distinct skill.
Opening Principles: Part One
18 hours ago