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Do Ideas Exist in Reality?

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In the last few Friday Philosophy posts we’ve been looking at the presocratics (that is, ancient Greek philosophers who lived and taught prior to Socrates). This week we’re moving on to a new category: the Eleatics. These philosophers are also presocratic, but are often grouped together separately as they all lived in the ancient town of Elea (present-day southern Italy). The first philosopher in this new mini-series is Parmenides.

Who Was He?

Very little is known about the life and background of Parmenides. He lived around 510-440 BC and the only surviving fragments of his work that we have are from a poem entitled On Nature. It is thought that he was a pupil of Xenophanes, who we looked at in this post, and was influenced by that philosopher’s thought.

What’s the Big Idea?

Parmenides is known for being the first philosopher to use deductive reasoning, a type of logic, in order to reach certain truth claims about the nature of things. His most famous argument is that it is impossible to know what is not. His reasoning behind this is that whenever you think of something, even something very abstract (like a flying spaghetti monster) the sheer fact that you have imagined it means it exists.

My Reflections

Thinking about the connection between thoughts, words, and things, is fascinating, so all credit to Parmenides for being a pioneer is this respect. Thinking abstractly about the connection between what is, and what is not, would later become a common activity of many well-known philosophers through the ages, from Aristotle to Wittgenstein.

However, it seems to me there is an important (and quite obvious) distinction between something existing as an idea, and existing in reality. To imply that everything we think of exists, is a somewhat misleading and erroneous concept. Thoughts have a type of reality, and then physical things have a different type of reality. Of course, it’s difficult to be 100% clear about what Parmenides meant from the few fragments we have, so I wouldn’t want to be too critical of his position.

Next Friday we’ll continue with the Eleatic thinkers and look at a big idea by Zeno of Elea. To ensure you never miss a post, please consider subscribing. Thank you for reading!


  1. In my consideration of philosophy, this was one of my favorites. The idea that we might bring something into being through the act of imagining is a leap toward divinity. Imagine the good (and the harm) we could do!

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  2. Xenophanes of Colophon (570BCE-480BCE) is my favorite pre socratic philosopher. At 25 he became a wandering poet and philosopher, although he is more known I believe as a theologian. His beliefs are still followed by many of us today, having ‘one’ God who is unmoving, but all seeing, hearing, and all thinking; common beliefs of his homeland area of Milesian Philosophers, attributing divinity to their physics. His physics (elements) were water and earth, believing that God holds the Universe together with thought, and may even be within physics.
    “True belief is that which you think you know”. Xeno finds God within the rationality of nature, not in poetic Mythology.
    I am enjoying your posts. Thank you.

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    1. Hi Philip!

      Thank you very much! I actually wrote a post on Xenophanes as part of my presocratic series, you can read the post here. But be advised that this philosophy series only aims to give a snapshot/taster, so there is, of course, much left out. But I’m happy for people to add their thoughts in the comments, as you have done 🙂

      Thank you for reading!


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