'Eidola' is the peeling away of images from an object that then enters the eye, in Democritus' theory of optics. However, given his atomic theory, it seems puzzling that he doesn't attempt to explain sight in those terms.

Does he in fact do so, or has this perhaps been done by a follower?
Or have I misinterpreted his theory of optics?

1 Answer 1


According to part 3 (Theory of Perception) of the Stanford Encyclopedia of Philosophy's Democritus page, his eidola argument is based on his atomist views.

Democritus' theory of perception depends on the claim that eidôla or images, thin layers of atoms, are constantly sloughed off from the surfaces of macroscopic bodies and carried through the air. Later atomists cite as evidence for this the gradual erosion of bodies over time. These films of atoms shrink and expand; only those that shrink sufficiently can enter the eye. It is the impact of these on our sense organs that enables us to perceive.

  • so eventually everything just slowly erodes away to nothing! Actually this is not so far fro the truth if you consider that light is made of photons - aka particles - and that an image of the body is carried into our eye by these photons. Aug 11, 2013 at 23:35
  • @MoziburUllah light is not a particle. It is theorized to be due to issues with other theories, so light was given a property to fit a certain accepted idea/agenda. But light can pass through a very thick transparent material because all light needs is a medium. If you remove a medium it becomes invisible. Hence why if you get into lower earth orbit you no longer see any stars. But once the light gets back into a medium (our atmosphere) stars can be seen again. No one has ever seen a photon let alone an atom or anything inside an atom. And I speculate they never will because of its properties. Mar 29, 2019 at 12:16
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    @autodidact: See wave/particle duality. Apr 2, 2019 at 2:40

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