Noun
Quality of being instantaneous.
Source: Webster's dictionaryDescartes maintained his confidence in the instantaneity of light. ... Yet in his derivation of the law of refraction, Descartes reasoned that light travelled faster in a dense medium than in one less dense. He seems to have had no qualms about comparing infinite magnitudes! Carl B. Boyer
Descartes maintained his confidence in the instantaneity of light. ...Yet in his derivation of the law of refraction, Descartes reasoned that light traveled faster in a dense medium than in one less dense. He seems to have had no qualms about comparing infinite magnitudes! René Descartes