Back to first principles

I call this method with which I approach life "back to first principles" without being entirely certain that that term is correct. I remember learning about first principles in maths class in secondary school and a lightbulb flickering on inside my head.
Here's a story to illustrate my meaning...

A new washing machine is delivered and needs to be installed. The old machine had both a hot and cold water input whereas the new machine only has one water input.

The installer rummages through the bits and pieces of plumbing attachments... he can't find what he's looking for. He wants to close off one of the inputs, to cap it. Something like this:

But WHY?! Why add to the detritus? This is the first step in a scenario that could develop into this...

So I suggested "going back to first principles". Remove the excessive y-junction and replace with a more simple piece of plumbing - a straight joint. Simpler than the cap with all the potential problems it can bring.

The installer was full of praise. Dumbstruck in the simplicity of the solution. Surprised by the "out of the box" thinking. And it seemed so obvious to me. More than obvious, it seemed the better solution.