The purpose of this paper is to explore Plato and Aristotle’s conceptions on knowledge, their understanding of the physical universe, and the suggestions that these beliefs conclusively made to the natural sciences. I shall do this by explaining Plato’s analysis of the nature of knowledge, and the role his proposed theory of forms plays in it. I will then go on to describe how this analysis applies to, and provides suggestions for, the methodology of science. This essay will then switch its focus to Aristotle, explore his views on motion, and describe how these represent a departure from Plato’s analyses. It will then conclude with the exploration of his understanding of motion, paying special attention to how it contributes to his understanding of the physical universe as a whole.
First, I will address Plato’s interpretation of knowledge. Plato believed that true knowledge could only originate from reason, and that reason could only be derived from that which is unchanging. However, he noted that the sense experiences which our world provides us with go through constant changes, and therefore cannot be relied upon as sources of reason. He states in his novel Timaeus, that these types of things are “opined by opining accompanied by irrational sensation” (Plato, and Kalkavage 58). Plato argues that the only way to evaluate sensory information to obtain true knowledge is through the application and analysis of certain principles that are unchanging. These principles are what Plato refers to as forms. Because of their unchanging nature, Plato regarded these forms as being able to be “grasped by intellection accompanied by a rational account” (Plato, and Kalkavage 58), and therefore undoubtedly true He concluded that believing to know something from only sensory information is not equivalent to having true knowledge of that thing. However, if forms cannot be understood from sensory information, one may wonder how a person can begin to comprehend these forms if it is not through perceptions and experiences. To address this puzzle, Plato suggests that before we were born in the physical world, we existed in the realm of the ideal forms. It is there where our soul gained true knowledge. Therefore since “the soul is immortal and has been born many times” (Plato, Anastaplo, and Berns 17), true knowledge always lies within the soul and learning is simply a matter of recollecting what our souls learned before.
Plato’s beliefs introduced a radical new way of thinking to natural scientists, specifically astronomers. His theory served as a warning to scientists that information derived from visual experience is not equivalent to having true knowledge of that thing. This is a revolutionary suggestion for the reliability of previous data collection methods, especially in the case of the conventional idea held in astronomy that knowledge could be derived from an expertise in visual observation of celestial motion. Plato gives two possible outcomes for scientists to consider when confronted with observational data. The first is to discern some unchanging, and therefore rational, mathematical structure within the data in order to obtain a true knowledge of what is seen. The second is to understand where irregularities in this data are too great to be able to discern any such mathematical structure. In this case Aristotle suggests that the data can only be thought of as simply a subject of reality, therefore unable to provide true knowledge.
Next, I will explain Aristotle’s views of the nature of change, and how they represent a departure from the methodology of Plato. Unlike Plato’s theory of forms, in which forms are unchanging and absolute, Aristotle believed that most substances undergo change in some way. Also, when describing change, Plato only recognizes change in a pair of opposites, but Aristotle elaborates on this idea, and describes five necessary components for change. In Book V of Aristotle’s novel Physics, he explains that “there is something which initiates the change, and something which is changing, and again something in which the change takes place (the time); and apart from these, something from which and something to which” (62). In simpler terms, Aristotle believed that every change has the following: a cause, some starting point, something which the change acts on, some ending point, and some time in which it occurred.
Aristotle also divided the different types of change he believed to occur into four different categories. The first being change in substance. This type of change encompasses transitions from existence to nonexistence, such as when something is born and when it dies. The second type of change that
can occur is a change in quality, also known as an alteration. Hot food becoming cool or the change in color of fruit would be an example of this type. The third type of change is that of quantity. This often refers to the growth or diminishment of a certain object. For example, a toddler goes through a quantitative change during a growth spurt when he grows taller. Finally, the fourth type of change that Aristotle acknowledged is change of place, otherwise referred to as motion.
Motion specifically played a large role in developing Aristotle’s overall understanding of the global features of the physical universe. Aristotle believed that knowledge came from understanding and being able to explain the causes which originated motion, or more generally change in itself. This presents the fact that Aristotle believed a physical explanation was necessary to obtain true knowledge, whereas Plato believed that true knowledge was not reliant on physical evidence. This led to Aristotle’s expansion of Plato’s geocentric model of the universe. Unlike Plato, who thought of it in geometric terms, Aristotle thought of this model as physically real and gave a physical explanation for it. According to Aristotle, all of the motion in this system originates in the outermost sphere. This motion is the ultimate cause of all motion in the universe. For this reason he calls the outermost sphere the prime mover.
To conclude, in this paper we explored Plato’s analysis of the nature of knowledge, specifically recognizing the integral role his proposed theories of forms played in it. This provided us with the basis to understand Plato’s views on the unreliability of the information we perceive in physical world. We then examined how this analysis provided a radical new way of thinking about the reliability of information obtained by sensory observation. Next, we examined Aristotle’s views on the nature of change, emphasizing how his understanding represents a departure from Plato’s ideas. We then looked more specifically at one of his four proposed types of change: motion. We examined the role it played in not only in his theory that all motion originates from the outer sphere of the universe, but also in his overall understanding of the physical universe.
Aristotle, Philip H. Wicksteed, and Francis Macdonald Cornford. The Physics. Cambridge, MA: Harvard UP, 1980. Print. Plato, and Peter Kalkavage. Plato’s Timaeus: Translation, Glossary, Appendices and Introductory Essay. Newburyport, MA: Focus Pub./R. Pullins, 2001. Print. Plato, George Anastaplo, and Laurence Berns. Plato’s Meno. Newburyport, MA: Focus Pub./R. Pullins, 2004. Print.