Distinguishing what is real and what is not is a part of life. But to distinguish one from the other, one must choose how. This choice is based on whether that person relies more heavily on their senses like George Berkeley, or their mind, like Descartes. Despite the differences, each way of knowing reaches a common goal, discerning the truth and what is believed to be true. The senses cannot give us a true representation of truth, so reason should be used. Using the knowledge issues to what extent can we achieve certainty starting with our own minds and to what extent do our senses give us knowledge of the world as it really is, how the different ways of knowing help us distinguish truth will be conveyed, answering how reason and perception can differentiate between something that is a justified true belief or something that is believed to be true. Senses merely form an idea of what truth actually is. The senses observe, but they cannot give one knowledge of the world as it truly is. For example, Copernicus lived in the 1500s, where people believed in the Ptolemaic model because it agreed with their senses. Ptolemy said that the earth was in the center of the universe and it did not move. People did not sense the earth moving, so they believed him. An empiricist, George Berkeley questioned material reality. He believed that we cannot know any more of the world than we perceive through our senses. If Berkeley had lived throughout this time, he would have perceived that the earth does not move. He thought that the only things that exist are the things that we perceive. Meaning, one cannot perceive the earth moving. But Copernicus believed in a heliocentric model, where Earth and other planets rotated around the sun. He used mathematics and reason to develop this theory. Copernicus too did not feel the earth, but he denied his senses. He knew that there were twenty-four hours in a day and as the year progresses, the seasons change. This led him to believe that the earth rotated on its axis as it rotated around the sun. The Copernican model was right. Proving that our senses are only a perception of what is true or what is believed to be. Sense perception cannot truly help us distinguish between what is true and what is believed to be true because it only gives us an idea of the truth. Truth comes by reason. To be certain, one needs reason because our senses will only take us so far. If something appears to be moving on its own, one’s senses would conclude that the object is moving on its own. But with reason, one would achieve certainty by knowing that objects cannot move by themselves unless acted on by an opposing force. We can achieve certainty with our