Ancient Greek Philosophy: Plato and Aristotle
Plato
Plato’s philosophy explores the world’s nature and the problems of humanity, including political, social, metaphysical, epistemological, anthropological, and moral-political issues. He aimed to understand the essence of things, the possibility of knowing that essence, human nature, and the ideal society. Plato synthesized the ideas of Parmenides and Heraclitus, addressing the problem of motion from the Pythagoreans, Socrates’ dualism, and inductive reasoning, while striving for universal definitions.
Plato’s philosophy is characterized by a dualistic worldview. He posited two realities: the sensible world (perceived by the senses) and the intelligible world (the realm of Forms or Ideas). He also distinguished between two types of knowledge: sensory knowledge (based on perception) and rational knowledge (based on reason). According to Plato, true knowledge is only possible through reason and concerns the Forms, which are eternal, unchanging, and perfect.
Plato believed that the universe was created by a Demiurge, an intelligent being who ordered the chaotic, eternal matter. Each individual thing in the sensible world is a copy of a corresponding Form in the intelligible world. The Forms are transcendent, meaning they exist independently of the sensible world. Plato argued that knowledge is possible only if there is something beyond the constant change of the sensible world. True knowledge must be infallible, objective, universally valid, and about the real, not merely about what is perceived by the senses.
Plato’s theory of knowledge involves the concept of reminiscence. He believed that the soul pre-exists the body and has innate knowledge of the Forms. When the soul is embodied, it forgets this knowledge but can recollect it through reason and philosophical inquiry. This process of recollection is called dialectics, a method of questioning and answering that leads to true knowledge.
Plato’s dualism extends to his anthropology. He believed that humans are composed of a body and a soul. The body belongs to the sensible world, while the soul belongs to the intelligible world. The union of body and soul is unnatural. The soul is immortal, exclusively human, and the principle of knowledge and intellect. Plato further divided the soul into three parts: the rational (representing reason), the irascible (representing courage), and the concupiscible (representing desires).
Plato’s ethics and politics are intertwined because he viewed humans as social beings. He believed that there is a correlation between the parts of the soul, the virtues, and the social classes. The rational soul corresponds to wisdom and the ruling class, the irascible soul to courage and the warrior class, and the concupiscible soul to temperance and the artisan class. Justice is the virtue that governs the relations between the parts of the soul, the social classes, and the other virtues. The highest Forms are the Good, the Beautiful, and the Just. Wisdom consists in possessing knowledge of these Forms. Plato believed that perfect happiness is unattainable in the material world and can only be achieved after death. He considered aristocracy (rule by the best) to be the ideal form of government.
Aristotle
Aristotle’s philosophy addresses the problems of movement, change, and the unity of being. He sought to understand the function of humans within the sensible world, unlike Plato, who focused on the realm of Forms. Aristotle believed that nature is teleological, meaning it has a purpose or goal. He argued that the end or purpose of humans is internal to them.
Aristotle agreed with Parmenides that something cannot come from nothing, but he believed that motion is possible. He explained motion as the actualization of potentiality. For example, a seed has the potential to become a tree, and this potential is actualized when the seed grows into a tree. The elements involved in change are matter, privation, and form. Aristotle distinguished between accidental change (where the substance remains the same) and substantial change (where the substance changes).
Aristotle’s theory of causes explains natural beings in terms of their internal and external causes. The internal causes are matter and form, which together constitute the substance of a being. The form is the essence of a thing, while the matter can be prime matter (which is not perceived by the senses and is common to all beings) or secondary matter. The external causes are the efficient cause (which produces the movement) and the final cause (the purpose or goal towards which the movement is directed).
Aristotle’s anthropology is also hylomorphic, meaning that humans are composed of matter (body) and form (soul). However, unlike Plato, Aristotle believed that the union of body and soul is natural and substantial. The soul is the actuality of the body, and the body is the potentiality of the soul. The soul is the principle of life, and the body is potentially alive. Aristotle rejected Plato’s notion of the soul’s pre-existence and immortality. He believed that the soul cannot exist separately from the body and that it perishes with the body. Aristotle distinguished between three types of souls: vegetative (responsible for nutrition and growth), sensitive (responsible for sensation and movement), and rational (responsible for reason and thought).
Aristotle’s epistemology emphasizes the importance of sensory experience as the starting point of knowledge. He believed that we can abstract universal concepts from particular sensory experiences. The second level of knowledge is imagination, which allows us to form mental images of things that are not present. The third level is understanding, which grasps the essence of things. Aristotle distinguished between two types of understanding: active intellect (which abstracts the essence of things) and passive intellect (which receives the abstracted essence). He divided the sciences into theoretical sciences (such as metaphysics, physics, and mathematics) and practical sciences (such as ethics and politics).
Aristotle considered metaphysics to be the first philosophy, encompassing ontology (the study of being) and theology (the study of God). Metaphysics studies being as being, considering what is common to all entities. Aristotle believed that the universe is eternal and eternally in motion. Therefore, there must be an unmoved mover, a being that causes motion without itself being moved. This unmoved mover is God, an immaterial substance, pure actuality, and absolute perfection. God’s activity is self-contemplation.
Aristotle’s ethics is closely connected to his politics because he viewed humans as social beings by nature. He believed that everything in nature strives towards an end or goal, the ultimate good. For humans, the supreme good is happiness, which consists in the contemplative activity of the intellect. However, humans cannot achieve the perfect happiness of God and must content themselves with a limited form of happiness. Happiness is achieved through virtuous activity. Aristotle distinguished between intellectual virtues (which pertain to the rational part of the soul) and moral virtues (which pertain to the appetites and desires). Virtue is a stable and voluntary disposition, freely chosen and based on reason. It is the mean between two extremes, one of excess and the other of deficiency. Happiness is the activity of the soul in accordance with perfect virtue. Humans can only achieve happiness by living in society. Aristotle preferred aristocracy as the best form of government and believed that the ideal city-state should be composed of middle-class citizens (a balance between the rich and the poor).