While studying Aristotle’s works on the nature of the universe and Earth and his overall ideas of natural physics one gets amazed of the achievement of human thought. By simple observations ancient philosophers have managed to come up with conclusions about the structure of the universe, size and shape of our planet etc. Although the development of the natural philosophy was slightly slowed down by the theological ideas of Middle Ages, there still were some significant thinkers that have developed and altered Aristotelian ideas.
The theory of four main elements of perception that can be combined into four main substances on Earth has been developed and implemented many times throughout ages. Aristotle’s “apparently simple bodies” (p. 540) are Fire, Air, Earth, and Water. These are so essential not only because they are comprised of the combination of moist, dry, hot and cold forms. But the four elements are also able to transform into one another, and this is another reason why Aristotle gives them so much attention. Lucretius further developed the theory of the four basic elements. But although he noted the existence of four basic elements, this philosopher has focused on the solid structure of matter. Lucretius considered the four elements “soft” because “void is a part of them” (p. 36). And he developed a theory of atoms – very small solid elements that compose all the matter. He believed that only atoms are eternal, as they do not consist of any parts being the smallest elements in the world. The ideas of these ancient philosophers were simply destroyed by the theological thought of the Middle Ages. For example, the “Condemnation of 1277” states that only God is eternal, He is the reason for all movements in the universe and creation of all things. Thus nature being the creation of God cannot be eternal, as well as its’ elements.
A very interesting part of Aristotelian natural philosophy is his ideas of the construction of the universe. By analyzing the notions of his predecessors, Aristotle has formed a number of opinions about the shape of Earth and structure and movement of the whole universe. Firstly the philosopher assumed that the Earth has a spherical shape. He came up to this conclusion watching the movement of objects thrown in the air and seeing the shape of the Earth as a reflection on the Moon during the eclipse. Moreover, he concluded also that the size of Earth is not significant in terms of Universe and it is definitely smaller than the stars (Aristotle, p. 489). Nicole Oresme, a famous philosopher of the Middle Ages, fully agrees with the idea that Earth has a spherical shape. And his further studies are based on this idea.
Movement of bodies in the Universe is another essential topic explored by Aristotle. The Ancient philosopher believed that while the Earth is immobile, all the “heavens have to move in one place” (Aristotle, p. 479). Therefore in the Aristotelian natural philosophy all objects in the universe, except of the Earth, were moving. Oresme has conducted a thorough analysis of this theory as well as of the opposing ones. One of the most interesting conclusions of the philosopher was that it is impossible to define weather only earth, or only the heavens, or even both are moving relying only on the observational experience. But as a main result he concluded that it would be more practical for one Earth to rotate instead of making all heavens turn around the planet. At the same time Oresme assumes that heavens also move, but at a slower pace. But despite all the philosophical and scientific arguments, there is a very strong theological element in the analysis. Together with physical reasoning and logical assumptions Oresme presents some parts from the Holy Bible that would justify the immobility of the Earth. When he comes up to a conclusion that the planet moves itself, the philosopher notes: “it would contradict the Holy Scripture… And it is also written of the earth that God made it motionless” (Oresme, p. 506). Therefore despite being a philosopher and a scientist, Oresme was still under a strong influence of theological doctrines and Holy Books.
The last essential part of Aristotelian theory of the Universe is the speed at which all the objects in heavens move. Aristotle noted that the universe is big and the objects that we perceive as small stars are in fact large bodies situated at far distances. The philosopher believed that stars are attached to circles and move along with their circles. Referring to the speed of the movement he stated “pace of each circle should be proportionate to its size” (Aristotle, p. 477). Therefore according to Aristotle, the speed of stars depended on the size of their circles. The second reason for the difference in star movement speed was the distance from earth. And the outermost stars, according to Aristotle, move the fastest, while the rest of the heavens moves at a relatively slower speed (p. 480). But Oresme has developed a totally contradictory theory. According to him, the further stars are located from earth, the slower they move. And Oresme believed in the existence of the “heaven of the fixed stars” (p. 508), which are either motionless or move very slowly. Therefore the theories of the philosophers on the speed of movement of heavens are not just different, but in fact propose two opposed ideas.
But not everyone had such progressive philosophical and scientific attitudes as Oresme. The “Condemnation of 1277” states that “heavenly bodies are moved by an intrinsic principle which is the soul… like an animal” (Klima, p. 184). In this case all the ideas of natural philosophy are ignored and replaced with theological notions and principles. Moreover, the same as Oresme, this document defines God as the main reason of motion of all elements in the universe.
Aristotle proposes a very unusual reason for the immobility of earth. He states that only something located in the center of everything is motionless. Therefore Earth is in the middle of the Universe. Aristotle supports this idea by noting that any objects thrown in the air return back to the planet. Moreover, he emphasizes that this is the reason why water and earth stay together, as they move towards the center, while air and fire on the contrary move away from the center.
Although Oresme believed that earth is actually moving, he had written almost the same words that Aristotle did, but not about the earth. The Medieval philosopher states “the noblest thing possible achieves its perfection without movement, and this is God Himself” (Oresme, p. 508). Therefore as the Aristotelian nature philosophy perceives the earth as the immobile center of everything, the same way Oresme’s theological education makes him put the immobile God in the middle. And despite the obvious difference in theories, both philosophers have created a very interesting idea of the immobile center of the universe.
Despite the period of Dark Ages that has covered Europe and the strong influence of church on the developments in philosophy and science, there were some educated specialists, who were developing Aristotelian thought. One of them was Nicole Oresme, who has not only studied the natural philosophy, but also developed and altered the existing theories. Therefore it would be unfair to state that the Middle Ages had a pure negative impact on the development of Aristotelian theories. That was rather a different perspective, which brought a number of new ideas to the natural philosophy theory.