Psychology is a science which finds its roots in philosophy. As a science, it uses theories, models and hypotheses to describe its findings. As a part of philosophy, psychology investigates many of the same issues as the early thinkers.
Every theory of psychology makes statements based on its own assumptions. These assumptions can be categorized on such dimensions as mind-body, subjective-objective, micro-molar and passive-active. Using these assumptions, each theory describes and explains how and why people behave as they do. Theories should be: clear, useful, have the smallest number of assumptions possible, summarize facts, be internally consistent, and have a heuristic function.
Theories often are so large that they can’t be tested all at once, and some only can be tested by inference. Indeed, strictly speaking theories are not tested at all. Theories are composed of constructs (ideas) which must be translated into measurable variables. These variables are organized as a model, and it is the model which is tested. Theories may contain postulates, laws, principles and beliefs, but models always have hypothesis.
Psychology was begun by individuals who were greatly influenced by their culture and times. It began as a personal affair, became a regional cluster of similar thinking people, and then developed into an international entity. It went from personal hobbies to systems of psychology.
Although early philosophers focused on cosmological questions, there was a transition to discussions of the mind and internal processes. During the Hellenic Period (600-322 BC), great individual thinkers emerged, including Thales, Phythagaras, Democritus, Hippocrites, Socrates, Plato and Aristotle. Borrowing from Empedocles, Hippocrates believed there are four basic elements: earth, air, fire, and water. He extended this analysis to the body by proposing four basic humors (bodily fluids): phlegan (earth), blood (air), yellow bile (fire) and black bile (water). Using these four fluids, Hippocrates identified four personality temperaments sanguine: (cheerful, based on blood), choletic (like the fire of yellow bile), phlegmatic (slow and full of phlegm), and melancholic (sad as a result of black bile).
Aristotle,a student of Plato, proposed a metaphysics where form and matter are inseparable in this world. Matter cannot exist without form, although form could exist without matter. In his writings (De Antima), Aristotle proposes that the psyche has a hierarchy of functions. The lowest level is vegetative, and is found in all plants and animals. Sensing and perceiving is a function of psyche found only in animals and people. This sensing process allows us to absorb the form of an object without absorbing its matter. Each sense was through a different media (taste through the flesh, smell through air and water, etc.). According to Aristotle, the sense which coordinates the information received from the other senses is called the common sense. Aristotle maintained that people are driven into action by appetite and needs but that they ultimately are self-directed by moral decisions and wishes (looking to the future). People alone are able to recollect (recall information), reason (tell right from wrong), and use mental laws of association (i.e., similarity, contiguity, and opposites).
After the death of Alexander the Great, the Hellenistic Period began and influence of Greek philosophy spread. This period included Epicurus, Pyrrho of Ellis, and Zeno. The philosophy of the skeptics and the stoics can still be found today.
The Hellenistic Period gave way to the influence of Christianity. For the first 300 years of its existence, Christianity was a small, isolated religion. Although persecuted by Nero, Domitian, Hadrian, and Marcus Aurelius, Diocletian (in 303 AD) became its protector, and by 395 AD, Christianity was the state religion of Rome. With an emphasis on the existence of a God who are personally concerned with human affairs, Christianity maintained every person has an eternal spirit which functions independent from the rest of nature.
Although not a Christian, Plotinus’ neo-Platoian approach presented the soul as an eternal, immaterial entity which thinks, perceives, and is separate from the body. Augustine was raised in a philosophically-mixed family (his mother was a Christian, his father was not). Converting to Christianity as an adult, Augustine advocated meditative introspection, denunciation of the flesh, and the importance of self understanding. Since true knowledge comes from God, examining the world is of limited value. For Augustine, the soul is composed of memory, understanding and will. Sometimes called the first of the Christian philosophers, Augustine’s views dominated western Europe for nearly 1000 years.
As civil wars increased, the Roman empire separated into western and eastern segments, and into contrasting philosophies. The West entered the Dark Ages, and the East embraced the teachings of Mohammed.
By the 11th century, the feudalism of western Europe had established three social classes: clergy, aristocracy, and peasants. The aristocracy owned the land which was worked by peasants in exchange for protection. As the population in the Middle Ages grew, peasants developed more skill and craftsmen guilds. This new social class of craftsmen/merchants was the basis of robust economy and marked the emergence of universities such as Oxford (1167), Cambridge (1209) and the University of Naples (1224).
The changing social order was accompanied by a philosophical shift. There was a re-emergence of classical Greek philosophy, modified by Christian thought. Combining Aristotle concepts and Christian doctrine, Thomas Aquinas proposed that each person is a specialized animal who possesses a soul. Body and soul are different but together in the same package.
For more on how philosophy and psychology work together, check out the free video series: If You Know Nothing About Psych