Impact

Use in the book

The earthquake explanation attributes violent shaking to the impact of exhalation increased and compressed within the earth. The pressure builds because moisture and cold obstruct escape. Impact is the resulting action on the surrounding ground, distinct from the earlier accumulation of material.

Places to read

1. I.36.2.5Confined exhalation moves the earth through impact.
2. I.52.10Meeting the object is a stage in a reported account of sight.
3. I.1.12aThe thunderbolt’s stroke expresses the power directing nature.

Translation in this edition

“Impact” keeps the causal action distinct from compression and from the shaking it produces.

Encounter with an object

Enstasis can name a standing against or encounter; elsewhere it may have a logical sense of objection. I.52.10 uses it in an account of visual rays meeting an object and returning to the eye. “Encounter” or “meeting” suits this optical context. The account is attributed to some Academics, and the noun “rays” is supplied in the text.

Blow and stroke

Plēgē is a blow, stroke, or impact. In Cleanthes’s hymn at I.1.12a, all nature trembles beneath the thunderbolt’s stroke. The bodily language of striking serves a theological image of divine power and government. It should be distinguished from the more narrowly mechanical collisions described in atomist accounts.