The text covers the perspectives, therapies, views, theories, and theorists building psychology throughout the generations from a casual observation into the advent of a scientific investigation. This investigation will discuss the earliest treatments of the mentally ill and how the treatment of the mentally ill improves over the years into modern psychology. This notable transformation can be seen in the definition of psychology changing from the study of consciousness to the modern definition as the scientific study of behavior, and in doing many theorists step forward to interpret not only behavior but also emotion and motivation as well. In existence is no set theory defining psychology or human behavior. In addition, in existence are a multitudinous number of polar theories regarding human behavior. The complexity of human behavior may make interpretation difficult; regardless, theories of psychology the basis of which is research and not opinion. When forming opin-ions on theories regarding psychology the research of the earliest philosophers and most notable psychologists of the 19th, 20th, and 21st centuries permits an individual to possess his or her own perspectives and views in regard to psychology and human behavior.