The definition problem

That difficulty isn't accidental. It's the core problem.

If you can't say what separates your reading from a calculator's arithmetic, you can't answer the question about machines either. So the obvious move is to define it: pin "thinking" down exactly, then test whether machines meet the standard.

Turing tried. It failed.

Say thinking requires processing information. Now your thermostat thinks. So does a spreadsheet.

Tighten it. Say thinking requires conscious awareness. Now you can't prove other humans think. You can't see inside their heads.

Every boundary you draw cuts the wrong thing.

So Turing did something cleverer still. He abandoned definitions altogether.