1.2 Greek Cosmology and Philosophy

Shortly after the conquest by Alexander in 331 BC, the Babylonian knowledge was transferred to the Greeks. Accordingly, Aristarchus presented the first known model that placed the Sun at the center of the known Universe with the Earth revolving around it, but his astronomical ideas were rejected in favor of Aristotle and Ptolemy whose geocentric model continued into the early modern age, until it was gradually superseded again by the current heliocentric model due the efforts of Copernicus, Galileo and Kepler in the 16th century.

Hipparchus and Ptolemy used complete list of eclipse observations covering many centuries, compiled from the Chaldean clay tablets recording all relevant observations of the various relations between the periods of the planets. These relations that Ptolemy attributes to Hipparchus in Almagest had all already been used in predictions found on Babylonian clay tablets.

In the earliest Greek literature we can find some references to various identifiable stars and constellations. Among others, the Hyades and Pleiads star clusters, and the constellations of Orion and Ursa Major, are mentioned in the Iliad and the Odyssey by Homer, hinting a rudimentary cosmology of a flat earth where stars rise and disappear into the ocean. However, in Pre-Socratic philosophy, Anaximander (610-546 BC) described a cylindrical earth suspended in the center of the cosmos, surrounded by rings of fire, while the Pythagorean philosopher Philolaus (480-405 BC) described the cosmos with stars and planets circling an unseen central fire.

The word “planet” in Greek means “wanderer” , because they were observed moving across the sky in relation to the other apparently fixed stars. The five planets: Mercury, Venus, Mars, Jupiter, and Saturn, can be seen with the naked eye, in addition to the Sun and Moon, to make a total of seven celestial objects that appear and disappear from time to time. Early Greeks thought that the evening and morning appearances of Venus represented two different objects, but Pythagoras (570-495 BC) is credited for realization that both were actually the same planet.

The Pythagoreans placed astronomy among the four mathematical arts, along with arithmetic, geometry, and music, while Plato proposed that the seemingly chaotic wandering motions of the planets could be explained by combinations of uniform circular motions centered on a spherical Earth. In his main books on cosmology, Timaeus and the Republic, he described a two-sphere model and said there were eight circles or spheres carrying the seven planets and the fixed stars.

In the 5th and 4th century BC, many celebrated philosophers shaped the Classical Greek philosophy, including Socrates (469-399 BC), his student Plato (424-348 BC) and his student Aristotle (384-322 BC). The first was “the first who brought philosophy down from the heavens, placed it in cities, introduced it into families, and obliged it to examine into life and morals, and good and evil.” Reale and Catan (1987). Plato was the most distinguished student of Socrates, and the primary source of information about his thinking that he presented in his dialogues. In his turn, Aristotle was also the most renowned student who joined Plato’s Academy, though he widely disagreed with him and criticized his theory of forms as “empty words and poetic metaphors.” Prior (2016).

In the 3rd century BC, Aristarchus, proposed a heliocentric model of the solar system, placing the Sun, not the Earth, at the center of the known Universe, hence he is sometimes known as the “Greek Copernicus” , but his astronomical ideas were not well-received. In his only work to have survived, he calculated the sizes of the Sun and Moon, and their distances from the Earth, but his results are drastically underestimated.

In the 2nd century BC, Hipparchus used the Babylonian observations and predictions to create better geometrical models. He is considered among the most important Greek astronomers, because he introduced the concept of exact prediction into astronomy, and he was the last innovative astronomer before Ptolemy. Among many other achievements, he developed trigonometry and produced accurate models for the motion of the Sun and Moon, confirming the accurate values for the periods of its motion that Chaldean astronomers are widely presumed to have possessed before him.

The geocentric model was predominant in ancient Greek philosophy as early as the 6th century BC. This model puts the Earth at the center of the Universe, while the Sun, Moon, planets, and stars, all circled around it in uniform motion. This is the apparent view from the perspective of local observers who see the Earth stationary, and the Sun revolving around it once per day, and also the Moon and other planets and stars, although some of these objects also have their own other motions. Furthermore, if the Earth is moving, we should observe the shifting of the positions of stars due to stellar parallax, which means that the shapes of the various constellations should change considerably from time to time across the year.

In reality, however, we do not notice the relative motion of stars because they are much farther away than Greek astronomers had ever thought. This stellar parallax was not detected until the 19th century after the inversion of modern telescopes. However, it might be appropriate to mention here briefly, that Ibn al-Arabi declared clearly that the stars are not fixed at all, and he correctly explained why we don’t observe their relative motion. He also clearly affirmed that the Earth is moving and rotating around its center, and explained why people don’t realize its motion, as we quoted many of his statements in Volume I.

Plato described the Earth as a stationary sphere at the center of the Universe, and the stars and planets were arranged in circular orbits, starting with the Moon and up to the celestial sphere of fixed stars. His student Aristotle added that heavenly bodies are attached to concentric crystalline spheres composed of an incorruptible substance called aether. Unfortunately, this concept of aether required it to have ideal physical properties that could not be conceived in terms of modern physics, especially after Michelson and Morley did not detect the aether drift as it was predicted.

The geocentricism was well established by the time of Aristotle, but the detailed model became standard only in the 2nd century AD, after it was developed by the Hellenistic astronomer Claudius Ptolemaeus, or Ptolemy (100-170 AD) who wrote many important books on astronomy and astrology, including: the Almagest, the Planetary Hypotheses, and the Tetrabiblos.

In his most influential work, Almagest, he explained how to predict the behavior of the planets, by introducing a new mathematical tool called the equant. He gave a comprehensive treatment of astronomical models and observations from many previous mathematicians, and he placed the planets in geocentric order that would remain standard in medieval astronomy until the 16th century when it was displaced by the modern heliocentric system. The main reason why Ptolemy’s model was successful is because he was able to explain the observed retrograde motion of planets.

As they wander in the sky, some planets slow down until they stop, and then they start to move backward in retrograde motion, and then again they reverse to resume their normal, or prograde, motion. In order to explain this, Ptolemy suggested that each planet moved in epicycle at the same time as it rotated around the Earth, so the planet moves around the epicycle, which in turn moves along the main path in its original revolution, which is called the deferent.

This geometrical combination of epicycles and deferents explained the observations mathematically, but it was actually not real. Nevertheless, it convinced most astronomers for the following fourteen centuries until the time of Copernicus.

Away from observations and physical cosmology, Parmenides (in the late 6th or early 5th century BC) was the first philosopher to question the nature of existence itself, challenging the previous theories and establishing the “Eleatic School” of philosophers who employed a method of axiomatic deductive arguments to justify their views that realty is one unchanging entity, and that multiplicity, motion and change are deceptive phenomena. Some of his famous successors in this metaphysical doctrine include: Zeno, Melissus and Xenophanes.

In his single renowned work, a poem called “On Nature” , survived only in fragmentary form, Parmenides described his dual view of reality: “the Way of Truth” and “the Way of Opinion” . In the first view, he explained that reality is one and unchanging, and existence is timeless and uniform, unlike what we normally observe in the world of appearances where our sensory faculties lead to conceptions which are false and deceitful, hence the second view. This led Democritus (460-370 BC) and other physicists to propose the atomic theory of matter, to contradict these arguments.

Parmenides attempted to distinguish between the reality of the unity of nature and its unreal variety or multiplicity. He had immense influence on Plato, who named a dialog after his name, and always spoke of him with veneration. In effect, Parmenides’ monistic views were deeply characterized in the whole history of Western philosophy, and he is often seen as its grandfather. In “Nature and the Greeks” , Erwin Schroedinger identified Parmenides’ monad of “the Way of Truth” as being the conscious self Schrödinger (2014), which was an important part of the development of Quantum Mechanics according to some interpretations, as we discussed in Chapter VI of Volume II.

However, Parmenides was not able to convince other prominent philosophers, such as Socrates and Aristotle, so his student Zeno tried again by reformulating the same argument in terms of what to become known as Zeno’s paradoxes, that can be considered the first thought experiments in which he demonstrated the deficiency of both the discretuum and continuum views. Zeno basically showed that both views will inevitably lead to infinity problems, which was in fact the main motivation that eventually lead to the development of calculus by both Newton and Leibniz as we shall see below.

We have already explained in a previous book Haj Yousef (2018), that there exists some remarkable correspondence between the metaphysical views of Parmenides and Ibn al-Arabi. Parmenides’ philosophy of monism, together with the complex and rigorous adaptation of his hypotheses in Plato’s Parmenides, constantly elaborated by the later Neo-Platonists, offer even closer analogies to Ibn al-Arabi’s overall ontological system, especially what came to be called later as the oneness of being, that led to the Single Monad Model of the Cosmos. One of the main principles of this eccentric cosmological model is the “Re-creation Principle” which postulates that the cosmos is being re-created every instance of time by the Single Monad, which alone may be described by real continuous existence, while everything else are various forms, or temporal imagery monads, brought into existence by this Single Monad that takes only one form at a time. Despite the apparent undeniable multiplicity of monads or forms, their existence ceases in the second instance after their becoming, and is perpetually replaced by other, usually analogous, forms. Therefore, Duality of Time, that results from the Single Monad Model, can be thought of as a mathematical formulation of the Ibn al-Arabi’s Oneness of Being, which is essentially the same as Parmenides’ monism that he expressed through his dual view of existence. Zeno’s paradoxes of motion and plurality has been discussed at length in Chapter II of Volume II.

As we mentioned above, Plato is the founder of the Academy in Athens, and he is widely considered the pivotal figure in the development of philosophy, along with Socrates and Aristotle, his most influential teacher and student, respectively. He also had noticeable influence on the Christian religion and spirituality, through many of his followers such as Plotinus and St. Augustine, the early Christian theologians and philosophers who played profound roles in the development of Western Christianity and philosophy.

Plato himself borrowed some of his main concepts from the Pythagoreans. He took their same mystical approach to the soul and its place in the material world, and the idea that mathematics and abstract thinking is a secure basis for philosophy. The Pythagorean numerical principle, that all things in the cosmos are numbers, can also be related to Plato’s view that the physical world of becoming is an imitation of the mathematical world of being, but this is also influenced by both Heraclitus and Parmenides. Form the first, through his famous remarks that all things are continuously changing, or becoming, as outlined in his well known image of the river with ever-changing waters where no one can swim twice, and from Parmenides who emphasized the idea of one changeless Being, and considered that change is an illusion of the senses as we have seen above. These ideas of becoming and being, led Plato to formulate his theory that there is a world of perfect, eternal and changeless forms; the realm of Being, and an imperfect sensible world of becoming that partakes the qualities of forms and their instantiation in the sensible world.

Plato’s denial of the reality of the material world is often coined as “Platonism” which means that the material world is only a shadow of the real world, as neatly demonstrated by the Allegory of the Cave, while the term “Neoplatonism” is applied to Plotinus (204-270 AD) and his followers whose philosophy is based on the three principles: the One, the Intellect, and the Soul, that led to the cosmology or cosmogony of “Emanationism” ; that all things in the cosmos are derived from the “first principle” , as opposed to both creationism (ex nihilo) and materialism (that all things, including mental aspects and consciousness, are results of material interactions). As Bertrand Russell noted, Plotinus’ philosophy had a great influence on the development of Christian theology:

“To the Christian, the Other World was the Kingdom of Heaven, to be enjoyed after death; to the Platonist, it was the eternal world of ideas, the real world as opposed to that of illusory appearance. Christian theologians combined these points of view, and embodied much of the philosophy of Plotinus. ... Plotinus, accordingly, is historically important as an influence in moulding the Christianity of the Middle Ages and of theology.” Russell (1945)

The “first principle” for Plotinus means a supreme transcendent “One” , containing no division or multiplicity; beyond all categories of being and non-being. He identified this “One” with the concept of “Good” and the principle of “Beauty” . Through these concepts, Emanation can be considered as an alternative to the orthodox Christian notion of creation ex nihilo. The first emanation from the One is Nous, or: Divine Mind, Logos, Order, Thought, Reason, or the first Will toward Good. From Nous then proceeds the World Soul, which Plotinus subdivides into upper and lower, identifying its lower aspect with Nature. From the World Soul proceeds individual human souls, down to matter, at the lowest level of being and the least perfected level of the cosmos, as he explained in The Enneads. These concepts are deeply characterized in later Islamic Cosmology and particularly that of Avicenna and Ibn al-Arabi.

Neoplatonism also influenced many medieval Muslim scholars, from the 9th century, beginnings with Al-Kindi (Alkindus, 801-873 AD), to the 10th and 11th centuries with Al-Farabi (Alpharabius, 872-951 AD) and Ibn Sina (Avicenna, 980-1037 AD). On the other hand, both al-Ghazali (Algazelus, 1058-1111 AD) and Ibn Rushd (Averroes, 1126-1198 AD) vigorously opposed the Neoplatonic views.

In general, on the concept of time, we can detect two clearly opposing views in the contrast between Plato’s and Aristotle’s schools of thought. Plato considers time to be created with the world, while Aristotle believes that the world was created in time, which is an infinite and continuous extension. Plato says: “Time came into being together with the Heaven, in order that, as they were brought into being together, so they may be dissolved together, if ever their dissolution should come to pass.” (Cornford 1997: 99). Aristotle, however, believes that Plato’s proposition requires a point in time that is the beginning of time and has no time before it. This notion is inconceivable for Aristotle, who adopts Democritus’ notion of un-created time, and thus he says: “If time is eternal motion must also be eternal, because time is a number of motion. Everyone except Plato has asserted the eternity of time. Time cannot have a limit (beginning or end) for such a limit is a moment, and any moment is the beginning of a future time and the end of past time.” (Lettinck 1994: 562).

Therefore, time for Aristotle is a continuum, and it is always associated with motion. As such, it cannot have a beginning. Plato, on the other hand, considers time as the circular motion of the heavens, while Aristotle said that it is not motion, but rather the measure of motion, though he also relates rational time and motion, but the problem that arises here is that time is uniform, while some motions are fast and some slow. So we measure motion by time because it is uniform—otherwise it can’t be used as a measure. To overcome this objection, Aristotle takes the motion of the heavenly spheres as a reference, and all other motions, as well as time, are measured according to this motion.

On the other hand, Aristotle considers time as imaginary because it is either past or future, and both don’t exist, while the present is not part of time because it has no extension (Lettinck 1994: 348).

Ibn al-Arabi agrees with Aristotle’s idea of a circular endless time and that it is a measure of motion, but he does not consider it as continuum, as we shall see later. On the other hand, he agrees with Plato that time is created with the world. In fact Plato was right when he considered time to be created, but Aristotle refused this because he could not conceive of a starting point to the world nor to time. Only after the theory of General Relativity in 1915, that introduced the idea of “curved time” , could we envisage a finite but curved time that has a beginning. By this we could combine Plato’s and Aristotle’s opposing views.