22 - Third Book. The World As Idea. Second Aspect.Paragraph 37 & 39

Schopenhauer used the word "will" as a human's most familiar designation for the concept that can also be signified by other words such as "desire," "striving," "wanting," "effort," and "urging." Schopenhauer's philosophy holds that all nature, including man, is the expression of an insatiable will to life. It is through the will that mankind finds all their suffering. Desire for more is what causes this suffering. He used the word representation (Vorstellung) to signify the mental idea or image of any object that is experienced as being external to the mind. It is sometimes translated as idea or presentation. This concept includes the representation of the observing subject's own body. Schopenhauer called the subject's own body the immediate object because it is in the closest proximity to the mind, which is located in the brain. (Summary by Wikipedia)