Plato is a Greek philosopher who lived in the 4th century BCE, while Thales, Anaximander, and Anaximenes were Pre-Socratic philosophers who lived in the 6th and 5th centuries BCE.

Thales believed that water was the primary substance from which all things originated and to which they eventually returned.

Anaximander referred to the fundamental substance as Apeiron, which means 'the boundless' or 'the unlimited'.

Anaximenes argued that air is the primary substance because it is capable of transforming into other substances, such as water and earth, through processes of condensation and rarefaction.

Pythagoras is primarily known for his mathematical discoveries, including the Pythagorean theorem and the concept of irrational numbers.

Heraclitus used the term 'Logos' to refer to the underlying order and reason that governs the universe.

Parmenides believed that reality is fundamentally one and unchanging, and that change and multiplicity are merely illusions.

Empedocles believed that all matter is composed of four basic elements: water, air, fire, and earth.

Anaxagoras proposed that Nous (Mind) is the primary organizing principle of the universe, responsible for order and purpose.

The Pre-Socratic philosophers' inquiries into the nature of reality, knowledge, and the universe laid the groundwork for the development of Western philosophical thought.

Democritus proposed that all matter is composed of indivisible and indestructible particles called atoms.

The Pre-Socratic philosophers were among the first to rely on reason and observation to understand the natural world, rather than relying solely on mythology or tradition.

The Pre-Socratic philosophers' ideas about the fundamental nature of matter and the universe have had a lasting impact on the development of modern physics.

The Pre-Socratic philosophers placed a strong emphasis on rational thought and reasoning as a means of understanding the world.

The Pre-Socratic philosophers' ideas are still studied and discussed in philosophy departments around the world, as they provide valuable insights into the origins of Western philosophical thought.