The Cartesian Maneuver

Descartes attempted this excavation. Strip away everything that could possibly be doubted. Senses? They deceive. Mathematics? Perhaps a demon manipulates your reasoning. Strip, strip, strip—until you reach bedrock.

Cogito ergo sum. I think, therefore I am.

Descartes' solution was God. A perfect being wouldn't deceive us, therefore our clear and distinct perceptions must be reliable. Convenient. Too convenient. He smuggled certainty back in through the same door he'd used to cast doubt out.

Most philosophers since have done the same—found their bedrock, then built upward so quickly they never noticed the cracks forming underneath.