Plato (424-347 BC) came from a wealthy family in Athens and was schooled mainly by sophists. Plato, however, wanted a modest teacher and found Socrates (470-399 BC). Socrates claimed that his only special wisdom was that he was aware of much he didn’t know. He wanted his students to appreciate what was true and permanent instead of temporary and popular. 

He did this by conducting dialogues with his students, to discover their inner capacities of finding truths. The fact that Plato chose Socrates and, therefore, philosophy still has consequences to this day. Socrates didn’t leave any written documents of his thoughts because, according to him, trusting in writing weakened the faculties of memory and serious thinking. Plato, however, made many written accounts of him: the Socratic dialogues. These emphasize the importance of the higher capacities of rational thinking and mathematical reasoning. 

The dialogues became the source of nativism - in which the innate is important, opposite to acquired qualities - and of rationalism, in which reason is emphasized. When Plato was 30, he founded the Academy, a place where pupils of different ages and interests could pursue their intellectual goals. 

In 367 BC, Aristotle (384-322 BC) arrived at said Academy and became a top student. At the age of 37, he left again. Aristotle placed much more emphasis than Plato on the systematic observation of the natural, empirical world of the senses. He became the first supporter of empiricism - the notion that true knowledge is obtained from sensory experiences of the external world.

Who were the pre-Socratic philosophers?

400 years before Plato's time, settlers from Greece spread and collected writings from wealthy Greek-speaking colonies. These colonies were developed very differently and had founded different types of governments. The Greeks, however, were all very proud of their language, and thought of all who spoke a language other than Greek as barbarians. 

Shortly before Socrates began teaching, Protagoras (490-420 BC) claimed that it was useless to speculate on big questions such as the ultimate nature and layout of the universe. He was a sophist and focused on purely human experiences and behaviour. The sophists tried to understand people.

Hippocrates (460-370 BC) is often mentioned as a pre-Socratic, and, like Protagoras and the Sophists, he dealt with everyday human concerns. However, Hippocrates was mainly a physicist. He attracted a school of students and followers, called the Hippocrats, who together produced many medical writings known as the Hippocratic Corpus. In this, diseases were described as natural phenomena, instead of the result of demons or supernatural influences. The Hippocrats had a ‘humoral’ theory to explain health and viewed disease as the result of the disbalance or four prominent fluids in the human body: blood, yellow bile, black bile and mucus – the Humors. The Hippocrats were responsible for some of the ethical, observational medical practices that we still see today. New doctors, for instance, have to take the Hippocratic Oath, promising to comply with ethical standards.

Who was Socrates?

As a young man, Socrates took up the profession of his father, a sculptor, and fought as a soldier. He married Xanthippe and they had three sons together.  He eventually made the career switch to a teacher which she was not happy about. 

Socrates differed from the sophists because he asked little to nothing for his services  and was shabby dressed. In addition to Plato, Xenophon (430-354 BC) was his best-known student. At the age of 70, Socrates was arrested by a new Athenian government, and was sentenced to death by drinking poison. Three of his students left descriptions of him, in which Xenophon described him as admirable and brave. 

Socrates' myth about reincarnation and memory is an extreme version of nativism, with the idea that fully formed but forgotten knowledge lies in the psyche, and it only requires empirical experiences to get it out. The ability to create abstract ideas lies in the human mind. According to this view, the path to wisdom is not to add opinions and experiences from the external senses, but to know yourself and to interpret these experiences the light of one's innate rational faculties.

What was Plato’s philosophy?

Legend has it that Plato's birth name was Aristocles, but because he had broad shoulders and was athletically inclined, he earned the nickname Platon (Greek for broad). Plato was about 25 when Socrates received the death penalty and died. He then fled from Athens to Italy but returned at the age of thirty. He founded the Academy there, where all different types of students were welcome. He was the leader of the school for more than 40 years. 

Plato himself was mostly concerned with the question of what was innate in the human mind and what the relationship between these innate characteristics and sensory experiences was. One of Plato's best-known answers to these questions was the distinction between appearances and ideal forms. An appearance (Greek: phenomenon) according to him referred to someone's conscious experience of something. Behind these apparitions, according to Plato, there was something more permanent: general and ideal forms that represent the essence of all objects. 

This is called idealism. One of Plato's most famous examples of idealism is the allegory of the cave. The reader is asked to imagine a group of prisoners, who are stuck in a cave with their faces towards the wall. Some men walk by the outside of the cave with some marionets on sticks, and because of the sunlight, the shadows of these puppets are projected along the wall of the cave. So, the prisoners only see the shadows on the wall and not the reality. The shadows are thus the metaphor for Plato's concept of appearances, and the real events the metaphor for his ideal forms. 

However, the story continues, and one of the prisoners is allowed to leave the cave. Gradually, he gets used to the daylight and learns to understand the relationship between the shadows and real events that cause them. However, when he comes back and tries to explain this to the other prisoners, the do not believe him, for all they know is the shadows on the wall. 

This enlightened prisoner, to Plato, equals to the true philosopher, the one who goes in search of true knowledge. The prisoners in a cave illustrate a fundamental case for modern psychology: the relation between conscious experiences of the external world and the objective nature of the physical stimuli that lead to these experiences.

Plato also claimed that the human psyche or soul consists of three elements: desire, courage and reason. In another famous metaphor, he presents these three elements as a charioteer trying to control a carriage drawn by two horses. One horse represents the desires and pulls in the direction of the fastest physical satisfaction. The other represents duty and the motivation to respond bravely to threats to the self or society. The charioteer is the rational component, that must try to lead the horses in such a way that they work well together.

Plato also believed that every psyche has these three components in different proportions, creating three general classes in a society. People who are dominated by the desires form the masses, those who are driven by courage are the soldiers who protect society, and the small minority dominated by reason is the elite that controls society. According to Plato, the proportions of the three components were hereditary. He therefore did not think that democracy was the best form of government. He was more for an oligarchy, a society led by a selection of elite people.

Who was Aristotle?

Aristotle was born in Macedonia. His father was a physicist, and the family doctor of the Macedonian king. At the age of 17, he was admitted to the Academy. The status of Aristotle's family was much lower than that of Plato. He crossed the sea to Asia, and came under the patronage of the local king Hermias. Aristotle married the niece of the king, Pythias. 

He was joined by Theophrastus (371-287 BC). They had already met at the Academy, and he first became Aristotle's student, then his friend. They did the first systematic observations together. Aristotle’s were of animals, Theophrastus’ of plants. 

After a few years Aristotle returned to Macedonia, becoming the tutor of the son of King Philip, Alexander. At the age of 20, Alexander became king, and his name became Alexander the Great. After this Aristotle returned to Athens and became the director of his own school, the lyceum. This school was broader than the Academy, and attracted hundreds of students, Aristotle wrote down all the results of their studies, so that more than 150 books were written by him. Many of these books have sadly been lost.

For Aristotle and Theophrastus, there were two essential steps in the accumulation of knowledge: cautious and extensive observations, followed by systematic classification into meaningful groups or categories. This became the beginning of stream taxonomy. For Aristotle, the cautious observation of the empirical world was the starting point for knowledge, but the mind had to turn these facts into a meaningful system of organized ideas and abstract concepts. Aristotle wrote his ideas down in his book 'about the psyche', which sometimes is seen as the first book on psychology. 

According to Aristotle, living organisms have psyches that vary in complexity. The lowest organisms are plants, which have two capacities that distinguish them from dead things: they feed and reproduce themselves. Nutrition and reproduction were therefore the two most fundamental functions of all psyches, according to Aristotle. This is sometimes also called the vegetative soul. The simplest animals have the additional capacity that they can move – locomotion - and to respond to their environment - sensation. Higher animals can also remember things and learn from their sensory experiences, the function of memory. These four functions are called the sensitive soul. The highest function of the psyche is only present in humans, which is the possibility to reason. This is called the rational soul. 

According to Aristotle, the human psyche possesses an innate set of categories in which memories of empirical experiences are classified and organized. These categories include substance (for example, a rock, a person or any other object), quantity, quality (colour, shape, etc.), location, time, relationship (larger, narrower, before, after, etc), and activity, meaning what it does (tell, hit, etc) or undergoes.

In summary, Plato and Socrates saw the human psyche as a reservoir of innate ideas and forms, which can be revealed or expressed through empirical experiences. Aristotle, on the other hand, emphasized empirical experiences as the necessary materials that the psyche processes on the basis of innate categories.

Who are Democritus, Epicurus and Lucretius?

Democritus (460-370 BC) formulated an atomic theory that included a limit on the divisibility of all material objects, and that they consisted of small, solid, unbreakable particles called atoms. According to him, atoms have different forms, and the universe consists entirely of an infinite number of atoms that move in space, the vacuum. Sometimes they collide and form new combinations, which form all physical substances in the universe. His atomic theory was attacked because he assumed that the interactions between atoms were random, which was contrary to the Greek assumption of causality, meaning that every event has to have a purpose. According to Aristotle, all events had four components: a material cause (the material of which something has been made), a formal cause (the idea or plan behind the thing caused), an efficient cause and the final cause (the purpose for which the thing was made).

Epicurus (341-270 BC) was a supporter of the theory of Democritus. According to Epicurus, people had to live a self-fulfilling life, free or pain and fear, in the presence of friends. According to his school, all objects in the universe consisted only of collections of atoms.

Almost nothing is known about the life of Lucretius (99-55 BC), but he celebrated the theory of Epicurus in a Latin poem entitled the Rerum Natura (about the nature of things). This contained the main ideas of Epicureanism in 200 pages, including atomism, modern hedonism, and the materialistic conception of the soul.

Who are three Islamic pioneers?

The Islamic Empire arose rapidly in the century after the death of Prophet Muhammad in 632 AD  and spread from West India to Spain and Morocco. Al-Kindi (800-871 AD) was born in Basra in Iraq  but moved to Baghdad at a young age. Here he became leader in the House of Wisdom, the equivalent of a research institute, whose members translated classical Greek texts into Arabic. Al-Kindi became known as the philosopher of the Arabs, through his scolarly comments on Aristotle. 

He also became known for his mathematical counting system in India, known as the Indo-Arabic numbers. This has led to important developments in the history of civilization. 1 to 9 were now displayed as all separate numbers, and the important '0' was added. This made it much easier to do mathematical calculations than with the Greek counting system. This also forms the source of the current word ‘algebra’.

Alhazen (965-1040 AD) lived in Cairo and wrote books on astronomy, mathematical theories of numbers, geometry, the theory of visual perception. His book of optometry consisted of seven parts and is still the foundation for visual scientists all over the world. He discovered that light from the outside world is reversed through the lens, creating an inverted image on the retina. Alhazen described the geometric properties of light and reflection device, the influence of binocular vision for depth perception, and psychological phenomena.

Avicenna (980-1037 AD) was born in the Persian city of Bukhara and spent most of his adult life in Iran. Avicenna left a personal document that became known for the lack of modesty. He became famous at the age of eighteen because he healed the local sultan with a vague illness, and as reward he has got access to the fantastic library of his patient. Here he learned all the metaphysical writings of Aristotle by heart. 

At the age of 21 he got a career in which he  analysed and wrote about the work of Aristotle. The Canon of Medicine consisted of 5 volumes about everything that Avicenna had learned about the discipline of medicine. The majority consisted of detailed empirical observations of diseases, and the most effective techniques for curing them. His second monumental work is called 'the book of medicine'. This was about all kinds of subjects that Aristotle had discussed and this work was meant to be a cure for ignorance instead of physical illnesses. Avicenna added to the receptive functions of the soul a motivating function, namely the desire. 

The desire gives the energy to approach desirable objects and avoid undesirable objects. Avicenna also deals with the rational soul of Aristotle. In his famous thought experiment of the floating man, he asked his reader to imagine a newly created but fully formed man in an empty space, whose senses are blocked and limbs so that he can neither touch nor move. Avicenna's question: without previously gathered experiences and without sensory organs, this man is aware of his own soul or himself? Avicenna's answer was: yes. For him, self-consciousness was an innate capacity of the human rational soul.

Around the year 1000, the contact between the Christian and Muslim world increased. Trade was a peaceful practise between the peoples, and in 1100 the Italian Leonardo Fibonacci (1170- 1240 AD) traveled with his father to North Africa. He learned everything about Al-Kindi's numerical system and became known for the Fibonacci series, in which each new number is the sum of the two preceding numbers. Mixing cultures also took place at locations on or near the borders of Christian and Islamic areas, for example in Toledo, Spain. The first university was founded in Bologna in 1088. The ideas of Aristotle were again appreciated by Thomas Aquinas (1225-1274 AD).

ExamTips

• Though the data are not important to the exam, it is important that you know the order in which the philosophers lived and who came before who.
• The three most important philosophers are Socrates, Plato and Aristotle. Make sure that you know their stories as well as how those three stand in raltation to each other
• Try to relate the psychology we study nowadays to how it was born out of the earliest philosophy.
• It helps to try and imagine the context in which these theories were born.