Plato's Theory of Forms and Knowledge

Plato's Two Realms of Reality

Sensible World vs. World of Ideas

On the other hand, we find the sensible reality, which is, as stated above, subject to change, mobility, generation, and corruption. Although its degree of reality cannot be compared to that of the Ideas (sensible things are not truly real), it is consistent and cannot be deemed nothing, unlike what Parmenides argued.

Overcoming Relativism and Ignorance

With this theory, the Athenian philosopher was able to overcome the moral relativism of the Sophists (whom, like his teacher Socrates, he sought to prove wrong, arguing that virtue is founded on knowledge, the so-called moral intellectualism). Similarly, the impossibility of scientific knowledge is surpassed. Science cannot be based on the constantly changing sensible world but must refer to something that does not change (the Ideas). Therefore, it would not be correct to base scientific knowledge on the senses as a criterion of truth, nor can we have true knowledge of what appears to the senses.

Similarly, the problem of the reference of universal terms would be resolved. Some philosophers believe universal terms refer to entities other than individuals because they can designate a plurality of objects. The entities correlated with universal terms are called Ideas. This theory would also resolve the Sophists' view of laws as mere convention; philosopher-rulers would be guided by transcendent, absolute ideals.

Plato's Theory of Knowledge

Plato's theory of knowledge is analyzed in several of his dialogues.

Knowledge as Reminiscence (Anamnesis)

Early approaches appear in the Meno and the Phaedo. In the Meno, Plato presents the theory of reminiscence (*anamnesis*). According to this theory, the soul, being immortal, has known everything in its previous existence. Therefore, when we learn something, what truly happens is that the soul remembers what it already knew. Contact with the sensible world and the exercise of reason are the instruments that trigger the soul's memory of true knowledge.

Mature Epistemology in the Republic

The mature approach to the problem of knowledge appears in the Republic, at the end of Book VI. Here, Plato establishes a strict correspondence between different levels and degrees of reality and different levels of knowledge.

Doxa (Opinion) vs. Episteme (Knowledge)

Plato primarily distinguished two modes of knowledge: doxa (opinion or sensible knowledge) and episteme (true knowledge or intelligible knowledge). To each corresponds a kind of reality: the sensible world and the intelligible world, respectively. True knowledge is episteme because it is the only knowledge that apprehends true being, that which does not change (the Ideas), and is therefore infallible.

The Divided Line and Cave Allegory

Plato uses the famous Analogy of the Divided Line and the Allegory of the Cave to illustrate the relationships between the two regions of reality, their divisions, and the corresponding types of knowledge.