"Physics investigates the essential nature of the world, and biology describes a local bump. Psychology, human psychology, describes a bump on the bump"

This quote by Willard Van Orman Quine is a contrast of the 3 sciences of physics, biology, and psychology. Physics is seen as the most fundamental science, investigating the vital nature of the world. Biology is seen as an action down, describing a local bump. Psychology, specifically human psychology, is viewed as an action down from biology, explaining a bump on the bump. This quote is a method of illustrating the hierarchy of the sciences, with physics being the most essential and psychology being the most particular. It likewise indicates that psychology is a subset of biology, which is a subset of physics. This quote is a way of emphasizing the value of understanding the basic nature of the world in order to comprehend the more particular elements of it.