Derek Parfit, one of Hume's most important defenders, addresses the puzzle of the problem of non-identity. Parfit states that there is no self. This statement is opposed to Ego Theory, which states that beneath experience there is a subject or self. Ego theorists state that the unity of a person's entire life, including life experiences, is also known as the Cartesian view, which states that each person is a "persistent purely mental thing." Parfit uses the split-brain case, which tells us something interesting about personal identity, to invalidate the ego theory. During the Split Brain procedure there are no “persons” or “persons” before the brain was split. In the experiment, the patient has control of his arms and sees what is in half of his field of vision with only one of his hemispheres. However, when the left and right hemispheres disconnect, the patient is able to receive two different written questions aimed at the two halves of his visual field; then, by hand, they write two different answers. In a split brain case, there are two streams of consciousness and Parfit says the number of people involved is none. The scenario involves the disconnection of the hemispheres in the brain. The patient is then placed in front of a screen where the left half is red and the right half is blue. When the color is shown to one hemisphere and the patient is asked, "How many colors do you see," the patient, with both hands, will write only one color. But when colors are shown on both sides of the hemisphere, the patient writes red with one hand, and blue with the other. There are two cases proposed by Parfit of the split-brain case that support the bundle theory and state that our belief... ...middle of paper......e.g. Therefore the mind mistakenly infers that this series of impressions is a persistent individual thing. Causality can also be explained by reusing the act of looking at a red shirt. When I look at a red shirt, I know it is red based on my previous perceptions or impressions. I then experience the sensation of the color red, which refers to my ideas that I have of that color. And then, when I look away, the memory of red still resides in my mind. In addition to causality, Hume also suggests propagation. Propagation is similar to regeneration in which sensations occur and then memories of those sensations follow. Therefore, due to causality and propagation, later stages of the mind are connected to earlier ones. But since time is continuous and constantly changing, everything can change, but what remains constant is the concept of causal continuity.