Plato’s Philosophy: Ontology, Epistemology, and the Theory of Ideas

Posted on Feb 28, 2025 in Philosophy and ethics

Plato (427 BC – 347 BC)

Plato’s Ontology and Epistemology

Plato’s philosophy has a political purpose: to design a perfect state that avoids continuous struggle and prevents the government from falling into the hands of those who prioritize private gain over the city. He envisioned a state where the death of Socrates, the greatest injustice, would not be possible. The Theory of Ideas is the fundamental reference point for all of Platonic philosophy, with three clear intentions:

  • Ethical Intention: Plato believed that virtue is based on knowledge; it is essential to know the Good to perform well. Plato asserts the existence of eternal and immutable moral concepts.
  • Political Purpose: Leaders must be philosophical, guided not by political ambition, but by ideas, particularly the idea of the Good.
  • Scientific Intention: Science can only deal with stable and permanent objects. Since all sensible objects are subject to change, only immutable and eternal ideas may be the subject of scientific research.

According to the Theory of Platonic Ideas, there are two radically distinct and separate worlds: the sensible world, where material things exist, dominated by the fate of which Heraclitus spoke, and the intelligible world, the world of Ideas, the only truly real world, which is immutable, immaterial, and eternal.

Ideas are the causes of all things and the foundation of all judgments we make about them. Material things are subject to permanent change and possess a precarious reality. We cannot say they “are,” but rather “have been” or “will be.” They are captured by the senses but are unintelligible.

The relationship between both worlds is described by Plato using the terms “participation” or “imitation.” All beautiful things participate in the Idea of Beauty, and sentient beings imitate particular ideas. Ideas are models that things seek to imitate without ever fully equaling them. Ideas are ideals that do not perfectly come to fruition in the sensible realm. The contrast between these two worlds is expressed in the dialogue Republic through the Myth of the Cave, which also affirms the absolute primacy of the Idea of the Good over all other ideas.

Plato’s Theory of Knowledge

Plato distinguishes between two forms of knowledge: knowledge or science, and opinion.

While opinion may be erroneous, science excludes the possibility of error. Knowledge aims to review the Ideas and aims at the world of sense.

Sentient beings “mimic” or “partake” of Ideas; the vision of those people serves as an occasion to remember. The process of knowledge is a promotion that requires effort, and in which successive levels can be distinguished. In the field of view, the lowest level of knowledge is imagination; above it lies belief, which studies sentient beings. In the field of science, and therefore the level of the world of Ideas, mathematics is placed as the first degree of scientific knowledge, which has value to start the soul of the world of becoming and direct it to the contemplation of Ideas. Lastly, dialectic, the culmination of knowledge, reaches a total and absolute knowledge to the supreme Idea, the Idea of Goodness.