Cartesian doubt

Cartesian doubt is a type of thinking that helps people figure out what is true and what is not. It was made famous by a man called René Descartes who was a philosopher in the 1600s.

He thought that the only way to really find out if something is true is to imagine the most extreme possibility and then question it until you have exhausted all other possibilities and can be sure.

Imagine you are trying to figure out if your teacher is telling the truth about something. You could use cartesian doubt to help you figure it out. You might imagine that your teacher is lying and then you would ask a lot of questions until you have investigated all other possibilities and can be sure that your teacher is telling the truth.