How do you know you know something, and why are you so sure that you do not know at times?

Where in the brain/mind do we decide we “know” something to be true – a mathematical equasion, or a linguistic anomaly, e.g. – not to mention philosophical dillemas – moral dillemas. Experience? It’s fluid and can be misleading. Seeing is believing? Ask a blind person.

How do you know you know, and why so sure?

Are you sure?