Some of the greatest minds have put together their own personal theories about human nature and how they arrived at their final decision. Human nature includes how people feel, think, and act and how they naturally acquire those resources. Culture and religion are often what fuel a person's innermost thought processes, and nature vs. nurture is a topic that many theorists have studied and formed an opinion on. The question of whether humans are born sinful or innately good has been debated for and against, and theories about why we are the way we are rage on. Sigmund Freud's theory of human nature stated that we are all very similar and pursue the satisfaction of basic needs. These desires are not limited to self-preservation, love, pleasure, and the avoidance of pain. Freud also theorized that feeling anger was neither good nor bad, but served the purpose of satisfying a basic need. This theorist claimed that humans are actually animalistic in their desire for self-preservation and that he saw no evidence of a humanistic instinct to seek perfection. He believed that we are simply more intelligent animals and that "homo homini lupus", man is a human being. Later the philosopher Avicenna would more fully adapt the theory that human beings are born pure and that with knowledge and life experience we begin to form a perception of the world around us. Philosopher John Locke also attributed that the beginning of human nature is like a blank slate and that we must “create our souls” through sensory experiences. With so many of the greatest minds believing that we are born “blank slate” it must mean that we are born without a preamble to immorality but learn about it through the world around us. Those who argue that our human nature is cultivated, rather than born in nature, also support the concept of “tabula