Socrates & his student, Plato, believed that the mind & body are completely separate entities, with the mind/soul living on past the body's death. Both philosophers emphasize that ideas & knowledge are things which come "pre-programmed" into us. Their theories are more in line with the nature side of the nature vs. nurture debate. They used logic & theoretical reasoning to support their ideas.

Aristotle disagreed with Plato & Socrates, saying that knowledge is something we acquire via our senses and through experience. His ideas support the nurture side of the nature vs nurture debate. He arrived at his ideas by relying on data & observations.

Descartes believed that the interaction between the mind & body was paramount to understanding the human experience. He did a lot of research into physiology, specifically on reflexes & nerves.

Locke proposed the idea that we enter the world as blank slates ("tabula rasa"). Anything & everything we become is the product of our experiences, putting Locke on the nurture side of the nature vs nurture debate.

Some key people transformed psychology from a philosophy into a science--a study that is founded on the scientific method as opposed to focusing on untested ideas.

Wundt set up the 1st psych lab in Leipzig, Germany. Inspired by the work being done in other fields at the time (e.g. Chemistry), Wundt wanted to discover the basic "elements of the human mind". He used introspection as his research method, and his efforts to break thought down into its smallest components laid the groundwork for Titchener's structuralism.

William James compiled the existing research of his time into the 1st psych textbook. Additionally, he used introspection as a way to develop his own theory of cognition--functionalism. James disagreed with Wundt's attempts to break thought down, and instead focused on thought as a unified stream of consciousness serving a higher adaptive purpose.

Titchener built upon Wundt's research and founded Structuralism as a psychological approach.

Mary Whiton Calkins studied with William James at Harvard, but was denied the Ph.D that her work had earned her. However, she did go on to become the American Psychological Association's 1st female president in 1905.

Margaret Floy Washburn, by researching animal behavior and publishing within this field, became the 1st woman to earn a Ph.D in Psychology.

While not a psychologist, Darwin's revolutionary ideas about natural selection greatly influenced the field. His theory proposed that behaviors & traits, as well as physical characteristics, are the product of natural selection and are adaptations that help the species survive & thrive.