Key Arguments

• He restates the essence of color in terms of its causal role and its dependence on light as the actualization of the transparent: 'For this is what the being is for color, namely, to be capable of causing movement in what is actively transparent; and the actualization of the transparent is light. 240 | 419 a 10 |'
• He offers an empirical indication: 'There is an evident indication of this. For if we place what has color upon the organ of sight itself, it will not be seen.' This shows that perception does not result from bare contact between organ and colored body.
• He then gives the mediated causal chain: 'Instead, the color causes the transparent—for example, the air—to move, and due to this, when the transparent is continuous, the perceptual organ is moved.'
• He criticizes Democritus’ theory about vision in a void: 'For Democritus did not speak correctly about this | 419 a 15 | in supposing that if the intermediate space became a void, we would see an ant in exact detail even if it were up in the heaven. 241 For this is impossible.'
• He argues generally from his account of perception as affection: 'For seeing comes about because the part that can perceive is affected by something. Now it cannot be affected by the color that is being seen [since it is at a distance]. It remains, then, for it to be affected by what is intermediate, so that there must be something intermediate.'
• He draws the consequence for a void: 'If the intermediate space became a void, | 419 a 20 | it is not that things would be seen in exact detail, but rather nothing would be seen at all.'

Source Quotes

This is also why it is not seen without light. For this is what the being is for color, namely, to be capable of causing movement in what is actively transparent; and the actualization of the transparent is light. 240 | 419 a 10 | There is an evident indication of this. For if we place what has color upon the organ of sight itself, it will not be seen.

240 | 419 a 10 | There is an evident indication of this. For if we place what has color upon the organ of sight itself, it will not be seen. Instead, the color causes the transparent—for example, the air—to move, and due to this, when the transparent is continuous, the perceptual organ is moved.

For if we place what has color upon the organ of sight itself, it will not be seen. Instead, the color causes the transparent—for example, the air—to move, and due to this, when the transparent is continuous, the perceptual organ is moved. For Democritus did not speak correctly about this | 419 a 15 | in supposing that if the intermediate space became a void, we would see an ant in exact detail even if it were up in the heaven.

Instead, the color causes the transparent—for example, the air—to move, and due to this, when the transparent is continuous, the perceptual organ is moved. For Democritus did not speak correctly about this | 419 a 15 | in supposing that if the intermediate space became a void, we would see an ant in exact detail even if it were up in the heaven. 241 For this is impossible. For seeing comes about because the part that can perceive is affected by something.

241 For this is impossible. For seeing comes about because the part that can perceive is affected by something. Now it cannot be affected by the color that is being seen [since it is at a distance].

It remains, then, for it to be affected by what is intermediate, so that there must be something intermediate. If the intermediate space became a void, | 419 a 20 | it is not that things would be seen in exact detail, but rather nothing would be seen at all. The cause, then, due to which color must be seen in the light has been stated.

Key Concepts

• For this is what the being is for color, namely, to be capable of causing movement in what is actively transparent; and the actualization of the transparent is light. 240 | 419 a 10 |
• For if we place what has color upon the organ of sight itself, it will not be seen.
• Instead, the color causes the transparent—for example, the air—to move, and due to this, when the transparent is continuous, the perceptual organ is moved.
• For Democritus did not speak correctly about this | 419 a 15 | in supposing that if the intermediate space became a void, we would see an ant in exact detail even if it were up in the heaven. 241 For this is impossible.
• For seeing comes about because the part that can perceive is affected by something.
• If the intermediate space became a void, | 419 a 20 | it is not that things would be seen in exact detail, but rather nothing would be seen at all.

Context

II.7 (419a8–20), where Aristotle articulates the role of the medium in vision and refutes Democritus’ void-based account of perception at a distance.