550 BC - Pythagoras - the mathematical mind.
Pythagoras (582-500 BC) suggested that matter and mind are mystically connected. Logic, numbers, spirit, and soul were expressions of the same reality. He thought the soul to be immortal and wandering on a path of transmigration from one body to another. The Pythagoreans had a geometrical conception of the world. They believed that mind is attuned to the processes of nature, in particular to the laws of mathematics. Mathematics is seen as the true essence of mind.
450 BC - Anaxagoras - the universal intelligence.
Anaxagoras (500-428 BC) introduced the concept of "Nous" (mind, reason) into Greek philosophy. Nous, the eternal mind, transforms chaos into order and through it the material world comes into being. The primordial One produces forms of multiplicity through dichotomisation. This process is originated and controlled by the power of mind, or Nous. According to Anaxagoras, mind is infinite and self-organizing. It is not intermixed with anything, but pure in its being.
450 BC - Alcmaeon - the dissected brain.
The Greek physician Alcmaeon (around 450 BC) concluded from his studies of dissection that the brain is the centre of intelligence. In doing so, he contradicted the mainstream theory of his time, which held that the heart is the centre of intelligence and seat of the soul. Alcmaeon also surmised that optic nerves conduct light from the eye to the brain and that the eye itself contains light.
400 BC - Hippocrates - the four humours.
Hippocrates (460-377 BC), the founder of Western medicine, is famous for the Hippocratic oath. He invented the notion of the four humours, black bile, yellow bile, phlegm, and sanguine, which he equated with the four elements. Hippocrates thought that disease arises from an imbalance of these four humours and that people can be healed by restoring their proper proportions. The dominating humour was also thought to be responsible for the temperament (black bile = melancholy, yellow bile = bitterness and irascibility, phlegm = equanimity, and sluggishness, sanguine = passionate and cheerful).
Hippocrates correctly identified epilepsy as a brain disorder. He held that not only thought and reason, but also feelings and moods originate in the brain: "Men ought to know that from the brain, and from the brain only, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, grievances, and tears. Through it...we...think, see, hear, and distinguish the ugly from the beautiful, the bad from the good, the pleasant from the unpleasant."
400 BC - Plato - ideal forms and reason.
Plato (428-347 BC) plays an important role in the history of epistemology. His theory of ideas, which he presented in the famous cave allegory, can be seen as a precursor of both medieval realism and later idealism. Plato held that all forms of the physical world are merely instances of perfect forms in an ideal world. The idea of a table is the supreme form of table of which there is only one. It contains in itself all actual tables of the physical world. The knowledge of ideas, or supreme forms, provides intellectual and ethical guidance for humans. Plato thought that perfect forms have an actual metaphysical existence.
Plato divided the human mind into three parts: the rational part, the will, and the appetites. Ideally the will supports the rational element, which in turn controls the appetites. If the rational element is not developed, the individual behaves immorally, hence immorality is a consequence of ignorance. Furthermore, Plato distinguished between two kinds of conscious thought: opinion and knowledge. He said that all assertions about the outside world are necessarily based on sense experience, and are therefore only opinions. In contrast, he described knowledge as a higher form of awareness, because it is gained from reason rather than from sense experience.
350 BC - Aristotle - the three souls.
Aristotle (384-322 BC) equated mind with reason and thought it to be a property of the living soul. In contrast to Plato, who believed that body and soul are two different entities, he held that mind and body are intertwined in all living beings and are thus inseparable. Growth, purpose and direction are therefore built into nature. Aristotle proposed three forms of soul: 1. the vegetative soul possessed by plants in that they grow and decay and enjoy nutriment, but they do not have motion and sensation, 2. the animal soul which bestows animals with motion and sensation, and 3. the rational soul which is the conscious and intellectual soul peculiar to man. Each higher form possesses in full the attributes of the lower souls, which makes human beings the only possessor of all three types. Aristotle also proposed a theory of memory surmising that the processes involved in short term memory (immediate recall) differ from those involved in long-term memory.
300 BC - Herophilus - the beginning of neuroscience.
The Greek anatomist Herophilus (335-280 BC) studied the human brain and recognised it as the centre of the nervous system. He distinguished the cerebrum and cerebellum and named the brain as the source of thought. Herophilus also made the first contribution to the field of neuroscience by distinguishing between sensory and motor nerves and by performing the most thorough study of brain anatomy attempted until the Renaissance.
300 BC - Pyrrho - scepticism as a state of mind.
The founder of the Greek school of scepticism, Pyrrho (360-272), stated that human mind is incapable of attaining true knowledge of anything, because ultimate reality is incomprehensible. Therefore, there is no objective knowledge, but only opinion. The best attitude one can develop in view of this fact, is to suspend any judgment completely, to free oneself from passions, and to calm one's mind. The idea that no person's judgment is more correct than that of another goes back to the first Sophist, Protagoras, who lived around 450 BC. Pyrrho developed scepticism into a more elaborate and consistent system of thought.
250 BC - Erasistratus - the brain and the vital spirit.
Erasistratus (300-260 BC) was an anatomist who worked one century after Aristotle. He found three tubular structures going to every organ of the body: an artery, a vein, and a nerve. He expanded Herophilus's theory of motor and sensory nerves by adding the thesis that all nerves are connected to and controlled by the brain. Erasistratus saw the brain as a mechanism for distilling the pneuma (the vital spirit), which he thought was flowing from the heart up to the brain and then down to the organs.
150 AD - Galen - the great Greek doctor.
Galen (129-199 AD) was the most influential physician of antiquity, after Hippocrates. He influenced medicine profoundly until about the 17th century. Galen synthesised the thought of Pythagoras, Plato and Aristotle and built upon the discoveries of Hippocrates and Erasistratus. He proved that the arteries carry blood instead of air (as the Greeks formerly presumed); and he demonstrated that the brain controls motion and voice. Galen further assigned the three largest organs of the body to be the seat of the three Aristotelian souls; the liver as the seat of the vegetative soul, the heart as the seat of the animal soul, and the brain as the seat of the rational soul.
For Galen, the rational soul was divided into the faculties of imagination, reason, and memory. He located these three faculties in the ventricles of the brain. Because the function of the brain was to distribute animal spirit throughout the body, to Galen it seemed that the fluid filled ventricles perform this function and thus disregarded the white and grey matter surrounding the ventricles. According to Galen, the brain receives vital spirit (pneuma) from the heart, which is mixed into the sanguine humour (blood). The brain then separates the animal spirit out and stores it in the ventricles, from where it is distributed throughout the body via the nerves. This mechanism of circulating pneuma controls muscles, organs, and all of the body's activities.
250 AD - Plotinus - the emanation of mind from the Absolute.
Plotinus (204-270 AD) rejected Aristotle's notion of the soul not being able to exist without the body. Building mainly on Plato, he said that mind is a prisoner of the body. Plotinus held that soul is the immortal part of mind. It survives the death of the body and enters a series of transmigration from one body to another. Consequently, the soul is the only abiding reality of the human condition. Plotinus formulated a theory of emanation according to which mind emanates originally from the Absolute Being, or the One, and then forms Nous, the universal intelligence, from which the world spirit is formed in turn. Human mind, animal mind, vegetative mind, and finally matter all emanate from the world spirit. They are different manifestations of one universal intelligence.
400 AD - St. Augustine - the illuminated mind.
The church father St. Augustine (354-? AD) had an interesting idea about mind. He said that the human mind couldn't gain knowledge from sense perception alone. He also rejected Plato's theory of ideas. Instead, according to Augustine, knowledge is acquired on account of divine illumination. He argued as follows: The shape of an object such as a tree can only be seen by the eye, because the object is bathed in light. Similarly the mind can only recognise truths, such as the mathematical truth 1+1=2, because it is illuminated by the light of eternal reason. This light is not so much the source of ideas and knowledge, but the condition under which mind is able to recognise the quality of truth. In spite of the simplicity of this idea, or perhaps due to it, Augustine had a tremendous influence on the philosophers and theologians of the Middle Ages.
