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Greek philosophers paid great attention to the elucidation of the content and the process cognition. Greek philosophy saw the purpose and the meaning of human life in the study of nature, as well as human essence. Let us recall the slogan of Socrates, according to which the meaning of human life is to gain knowledge (Socrates, n.d.). How does a man perceive the world? Is this world out of the human mind? These issues were of great interest to all philosophers of ancient Greece, including Plato and Aristotle.

It must be admitted that their theories of knowledge played a significant role in the further development of philosophy since they became a powerful impetus to the development of gnoseology (Horrigan, 2005). Both Plato and his student Aristotle propounded some arguments about knowledge. For Plato, learning is a recollection of our previous souls’ knowledge, while for Aristotle knowledge is gathered by practicing and doing. In this essay, these two arguments about knowledge will be compared.

Plato’s and Aristotle’s Theories of Knowledge

Plato's doctrine of knowledge is inseparable from his doctrine of being, as well as from his psychology, cosmology, and mythology. Plato reveals his theory of knowledge by means of a myth. According to Plato, the human soul is immortal. Before falling to the ground and receiving a corporeal shell, the soul contemplated the true being and kept the knowledge of it. By asking and answering questions, one can gain knowledge in itself, which means to “remember”. Therefore, according to Plato, the essence of the process of knowledge, is recalling by the soul the ideas that she had contemplated once upon a time. Plato wrote that “as the soul is immortal – as it has been reborn, time and again, and has seen both the things of this world and those of the underworld and all matters – there is nothing it has not learned” (Plato, 2002, p. 13). Thus, the nature of the soul must be akin to the nature of "ideas."

Only thinking might give the true meaning. Thinking is independent of sensory perceptions, as it is an independent process of remembering. A sensory perception can only generate an opinion about things, but not knowledge. The process of learning is defined by Plato as a dialectic, that is the art to conduct an oral hearing, as well as to ask questions and answer them, evoking memories. In other words, this reasonable apprehension of the ideas is the "perfect knowledge". Plato's dialectic is the path or movement of a thought from untrue to true. It is a thought, which has a contradiction in itself, that can cause the soul’s meditation (The Republic). According to Plato, knowledge is not possible for everyone. Philosophy as love to wisdom is not possible for both those who have the true knowledge (gods) and who know nothing at all (ignoramuses). A philosopher is the one who stands between full knowledge and ignorance and seeks to rise from less perfect knowledge to perfect one.

Plato's gnoseology is idealistic. In my opinion, the theory of knowledge, presented by Aristotle, seems to be more reasoned and thorough. Unlike Plato, Aristotle saw the basic level of knowledge in perceptual knowledge by which one might know about the certain existence, master the individual, and then make the ascent to the knowledge of principles (Shields, 2008). Aristotle not only emphasized the role of sensory perception but also tried to understand its mechanism. In contrast to Plato, Aristotle stated that universal could be known not based on intuition or “memory”, but only through the knowledge of the individual. Aristotle argued against Plato on this issue and showed that Plato’s doctrine of the world of ideas prevented one from understanding the reality. Aristotle saw the aim of science in the full definition of the subject, which is achieved when using both induction and deduction (Aristotle, n.d.). Aristotle considered philosophy as the love of wisdom, the highest form of science believed.

The essence of Aristotle’s protest against the gnoseology of Plato is in the main Aristotle’s thought, according to which general ideas do not exist apart from the world of things. They exist in the things themselves. I suppose that Aristotle was a moderate idealist. He came to the conclusion that general ideas were in the things on the grounds that for example, people, despite their differences, have something similar that defines them all as human beings.

Thus, the general ideas exist in things and not separate from them. For this reason, science as a discipline, which recognizes common ideas and based on them formulates the laws, has every right to rely on sensory experience as a source of knowledge. Aristotle's logic seems to be more consistent than the one of Plato. Moreover, for Aristotle, scientific or reliable knowledge is not the result of faith or subjective experience. It is the result of logical thinking, aimed at an opening of the causes and elements of what is given to a scientist in his/ her immediate sensory experience. Conclusion

The theories of knowledge presented by Plato and Aristotle provide an excellent opportunity to answer the question about the nature of knowledge, including scientific knowledge. Moreover, their main ideas are aimed at clarifying issues about how one might distinguish the true knowledge from the false one. Their methods proposed by them, namely the idealism of Plato and Aristotle's practical philosophy, are two different ways of grasping the truth. If Plato spoke of the conceptual ascent to the truth in the process of a dialogue, Aristotle pointed to the importance of sensory experience, which should be processed by means of logical thinking.

Thus, Plato's strong point is in his indicating the need to study the general ideas, because as we know, most science disciplines are aimed at formulating general laws and principles based on general ideas. At the same time, the extreme idealism of Plato and his negative perception of sensory experience can be seen as the weakness of his theory, because sensory experience gives a man the first knowledge about the world. Considering the gnoseology of Aristotle, one should admit that its strength lies in defining the sense experience as the primary source of knowledge. In addition, Aristotle’s merit is that he states the need to verify the empirical experience using logical reasoning. The weak point of Aristotle’s theory can be seen in his idea that true knowledge is always the knowledge of general ideas. In my opinion, this idea greatly reduces the notion of true knowledge, as there are situations when a researcher is not interested in the general ideas, but a particular phenomenon, as he/she does not need to formulate general laws, principles, and so on.


Aristotle (n.d.) Nicomachean ethics. Retrieved from http://classics.mit.edu/Aristotle/nicomachaen.html

Horrigan P. G. (2005). Philosophy of knowledge. Retrieved from http://www.horrigan.angelcities.com/knowledge.htm

Plato. Meno (2002). Retrieved from http://www.ma.utexas.edu/users/rgrizzard/M316L_SP12/meno.pdf.

Plato. The Republic (2002). Retrieved from http://www.idph.com.br/conteudos/ebooks/republic.pdf.

Shields, C., Aristotle, The Stanford Encyclopedia of Philosophy. Retrieved from http://plato.stanford.edu/entries/aristotle/.

Socrates (n.d.). Encyclopædia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/551948/Socrates