Key Arguments

• He connects the fate of organs under excess to his definition of the capacity as a ratio: 'It is evident from this why it is that excesses in perceptible objects destroy the perceptual organs (for if the movement is too strong for the perceptual organ, | 424 a 30 | the ratio is dissolved—and this, as we saw, is the perceptual capacity—'.
• He explicitly identifies the ratio with the perceptual capacity: '—the ratio is dissolved—and this, as we saw, is the perceptual capacity—', so when excessive movement breaks that ratio, the capacity is lost and the organ is destroyed qua sense-organ.
• He illustrates the point by musical analogy: 'just as the consonance and pitch [of a lyre] are if the strings are struck too forcefully). 286' The tuning (consonance, pitch) is a ratio in the string’s tension and length; a violent blow disrupts this structure, paralleling how an excessive sensible shatters the organ’s proportion.
• This explanation presupposes his earlier doctrine that sense-organs are means between contraries structured by a precise logos; extreme stimuli push them beyond the mean and thereby ruin their structure.

Source Quotes

It is the same [as the capacity], but the being [for it] is distinct. | 424 a 25 | For what does the perceiving would be a spatial magnitude, but surely neither the being for what is capable of perceiving nor the perceptual capacity is a spatial magnitude, but rather a sort of ratio and capacity of the former thing. 285 It is evident from this why it is that excesses in perceptible objects destroy the perceptual organs (for if the movement is too strong for the perceptual organ, | 424 a 30 | the ratio is dissolved—and this, as we saw, is the perceptual capacity—just as the consonance and pitch [of a lyre] are if the strings are struck too forcefully). 286 And also why it is that plants do not perceive, although they have a part of soul, and are affected by tangible objects (for in fact they are cooled and heated). For the cause of this is their not having a mean, nor a starting-point of a sort | 424 b 1 | that can receive the forms of perceptible objects; on the contrary, they are affected [by the form] along with the matter.

Key Concepts

• It is evident from this why it is that excesses in perceptible objects destroy the perceptual organs (for if the movement is too strong for the perceptual organ, | 424 a 30 | the ratio is dissolved—and this, as we saw, is the perceptual capacity—just as the consonance and pitch [of a lyre] are if the strings are struck too forcefully). 286

Context

II.12 (424a27–30), where Aristotle draws an immediate consequence from defining the perceptual capacity as a ratio in the organ, using the example of a lyre’s tuning to explain how excessive stimuli annihilate sense-organs.