In 1943 a psychologist named Abraham Maslow suggested that human beings have a hierarchy of needs, with needs at the bottom required to be fulfilled before the needs above can be attended to. In his revolutionary theory, the basic needs required for survival such as food, water and warmth are at the bottom, whilst the more emotional and higher-minded needs are at the top. Once the base layers have been taken care of, humans can pursue activities like writing a novel, singing in a choir or engaging in philosophical discussions.