The Dominican monk Thomas Aquinas in Italy was a prominent Scholastic theologian--one of the most influential thinkers of the Catholic Church of his time. He greatly influenced later theologians. Aquinas moved away from allegorical biblical interpretation and promoted the literal reading of Scripture. Aquinas and the Scholastics relied heavily on the ancient Greek philosopher Aristotle, whose work came to the Latin West from the Arab world. Aquinas believed in a logical, natural order created by God, which included Christian history.
Philosophers were the first to ask questions about psychology. The Greeks and later philosophers formed theories about how people can perceive the world, what is innate and what is learned through experience, and whether illnesses were physical or mental in nature. In the 1600s, philosophers pondered if the mind and body were separate and the mind unobservable or if the two were connected and both scientifically observable.
Monism Versus Dualism
Psychology has also been influenced by basic arguments about the very nature of reality. Ancient notions that all which exists is of one nature are collectively referred to as monism. Later, religiously-popularized notions that there are two kinds of reality in existence are referred to as forms of dualism. Both monism and dualism have left undeniable marks on the modern sicience of psychology.
Dualist ideas about human nature were first detailed by the Greek philosopher Aristotle(384-322 BC), who conceived of the soul as the animator of all beings, including humans. According to Aristotle, humans have rational(reasoning) souls. Humans' ability to reason makes human thought abstract, separate from the material world. Thus a human being has a material body but a rational(reasoning) mind, and is governed by two systems of nature. Artistotle's dualism explains human thought and action as unique in all existence.
Thomas Aquinas(AD 1227-1274) extended Aristotle's dualistic view of human nature with the argument that, because human thought is rational, human action is freely decided instead of compelled by natural forces. This is the essential argument in favour of free will. Whether human will is free or not is an important consideration in determining the morality of human action.
The most articulate proponent of the dualism of human nature was French philosopher Rene Descartes(1596-1650). Famous for the dictum Cogito ergosum ("I think, therefore I am"), Descartes distinguished between the free will that governs the rational human soul and the physical "passions"(appetites) and "emotions"(excitements) that govern the material body. Further, Descartes saw the realtionship between body and soul as a conflict, an ongoing struggle for control of one's actions.
Modern psychologists continue to debate the nature of human behaviour, with strong arguments both for forms of "free will" and for a more mechanical understanding of psychological processes.
Some of the earliest systems of philosophy were monistic pshilosopheis, advocating that all of reality has but a single nature. one form of monism, idealism, argues that all of reality exists only in the mind, as ideas, and thus things are "real" only to the person who is presently experiencing them. One extension of this idealism is that, for things to continue when no one is thininking about them, they (and we) must all be figments of a supreme being's imagination -- ideas of God, for example.
Another form of monism is materialism, arguing that the single nature of reality is matter. If all of reality is matter, then all that exists must be governed by the laws fo matter, or the laws fo mechanics. This view, known as mechanism, can be applied to human nature if one accepts that human beigns, like all else in reality, are purely material beings, and thus human action is governed by the physcial laws of mechanics. Mechanism has had an enduring influence on the science of psychology, especially in early theories about the relationship between bodily(physical) events and mental experiences.
One implication of mechanism is that, according to the laws of mechanics, physical forces cause specific changes in other physical objects. Causes determine effects in the physical world. If one wishes to understand the present condition of an object or event, one must examine the events(causes) which led up to (determined) it. This understanding -- that present conditions can be understood if one examines past influences -- is known as determinism. It is a critical assumption in any science.
Another essential tenet of science is the reliance on observable events as evidence of reality. Instead of imagining how things "must" be, a scientist observes how they are, or rather how they look, sound, feel, taste or smell. This reliance on the evidence of one's sensory experiences is known as empiricism.
Empiricism is such a familiar and common-sensical part of the scientific method that it is difficult to remember that the scientific way of knowing was once a new concept. Ancient and medieval scholars often argued that one could "reason" one way to the truth, or be informed through revelation, prophecy, or inspiration.
The English scholar Roger Bacon(1214-1292) argued that empirical observation was essential to the scientific method. Later, John Locke(1632-1704) asserted that empirical (sensory) experience was the basis for all knowledge. Locke maintained that the human mind at birth is a tabula rasa("blank slate") on which experience alone can inscribe knowledge.
Locke's influence continues with modern psychologists who argue that the way an individual is educated and nurtured vastly outweighs the power of any inborn talents or inherited nature.This "nature versus nurture" controversy has influenced many fields and topics in psychological research.