Kelly asked:

Heraclitus and Parmenides state contradictory views, both based these on their intuitions and then argued for them. It creates a crisis in ancient natural philosophy that the Pluralist attempt but fail to resolve. Ought we to give up on finding knowledge and follow opinion? Ought we to learn the skill of rhetoric to win the day for our point of view?

Answer by Caterina Pangallo

When we look back at these few presocratic philosophers, we can see that their main preoccupation was with three principal ideas: substance, the One and the Many. What they thought and the ideas they put into the world, are still today considered fundamental.

Because they put all these questions in a form which we still recognise as binding on us. Who are we? What’s out there? What is everything made of? What is matter, and what is life?

They observed nature and asked those questions; and we continue to build on their questions. We also still accept many of their notions of how things work – for example the vortex of Anaximander is no stranger to astronomers who see spiral galaxies creating worlds throughout the universe; the ‘fire’ of Heraclitus reappears in the conservation of energy; the immutable substance of Parmenides is the idea of a quantum world in which our observations are ‘our’ world.

The Presocratics got rid of anthropomorphisms, because they believed that human reason could explain the world. In my opinion this is one the most important changes that ever happened in human history. It could be said that the Presocratics taught us how to think. So there is your answer about rhetoric. You don’t learn anything just by using fine words.

All three: Heraclitus, Parmenides and Pythagoras wrestled with the idea of nature and each came up with a different solution. And now it is extremely interesting and noteworthy for the whole history of philosophy that all three answers which these philosophers gave are still acceptable, in one form or another, to us today. So these are the true prophets of philosophy — as well as of science.

They did not solve their problems forever. But they opened the doors to a better understanding of natural processes. This is fundamental, in order to acquire knowledge. Knowledge never ends, it’s a continuing process of discovering the world and humans in it.

So don’t assume that these are merely opinions. The difference between opinions and real knowledge is every Tom, Dick and Harry can have opinions, but you’ve got to admit that most people’s opinions are just presumptuous and very few very people have opinions of their own. Most opinions are just what someone else said. And what do they know?

But ideas like those of the Presocratics are ideas on which the human world can build. The world does not stands still until we have discovered everything there is. But in the meantime we can acquire real knowledge, and carry on from there.