The Ontological Counterrevolution: Parmenides, the First Extreme Rationalist

This post is one in a series on the Epistemology and Worldview Throughout History

Previously in this series: The Ontological Revolution: The Proto-Skepticism of Heraclitus.

As discussed in the previous post in this series, Heraclitus introduced ontology into the world of philosophy, threatening to upend the cosmological systems of his Milesian predecessors.  Not only did philosophers not know how things came to be, he seemed to say, they did not even know what it meant to be, because being was a matter of flux.

Just as the purposeless universe of the Milesians may have disturbed Pythagoras, so perhaps did the unstable and unknowable universe of Heraclitus trouble another brilliant thinker: Parmenides of Elea.  Parmenides responded by not only denying Heraclitus's doctrine of flux, but by going all the way to the opposite extreme.  He insisted that nothing EVER changed: that change is an illusion.  He attempted to prove this remarkable assertion by turning ontology, the study of being qua being, back upon the changing world of Heraclitus.  His argument for this went something like this:

1. Thinking requires an object.  When one thinks, he must think about something.
2. Therefore, one cannot think about nothing.
3. To think about a thing not being is to think of nothing.
4. Therefore, one cannot think about a thing not being.
5. Change implies a thing once was not, or is no longer.
6. Therefore, one cannot think about change.
7. Therfore, one cannot speak of change
8. Therefore, natural philosophy is nonsense.

What is exceedingly remarkable about this line of thought is not just its use of ontology, but its use of extreme rationalism. Vernon J. Bourke thought of rationalism as a school of thought "in which the criterion of the truth is not sensory but intellectual and deductive"¹. Perhaps inspired by the deductive geometric research going on at the time, Parmenides attempted to apply what Aristotle would later call the "syllogism" (deductions) to concerns that go far beyond abstract shapes.  He attempted a "demonstration", Aristotle's term for a syllogism which said something about the real world.  And here, at the dawn of rationalism, we have a paradigmatic instance of the tendency of rationalists to arrive via deduction at conclusions that wildly affront common sense.  The rigorous nature of deduction supposedly gives them licence to do so.  Parmenides offered a stark contrast to the observational (empiricist) methods of the Milesians and Heraclitus.  His distrust of the senses and reliance on pure ratiocination, however contentious-seeming the conclusions may be, can be seen in the following quote, which he ascribes to the goddess who puportedly showed him the "way of truth":

But do restrain your thought from this path of inquiry, and do not let habit, born from much experience, compel you along this path, to guide your sightless eye and ringing ear and tongue. But judge by reason the highly contentious disproof that I have spoken.

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¹Bourke, Vernon J. (1962), "Rationalism", p. 263 in Runes (1962).