Descartes' method of radical doubt consists of a process of a doubt. The four methods of radical doubts are: 1) only except clear/distinct ideas; 2) divide your problems into smaller, more manageable parts; 3) order your thoughts from simple to complex; 4) and check your results for errors.
Descartes uses this method to question his beliefs in the 1st Meditation by accepting the fact that most things we learn in life come from or through our senses. At times, our senses can deceive us, but only with small or far away objects. Our senses rest between primary and secondary qualities. By questioning the distinction of this primary and secondary quality, Descartes must doubt the reliability of his senses. For Descartes, to have doubts about his senses, he must find a reason to doubt both his primary and secondary perceptions. Descartes begins his process of doubting by putting out the optical illusion, which