Full Idea
The sensory idea of green (made of blue and yellow) is a confused idea, like the swift rotation of a cog-wheel which makes us perceive an artificial transparency, and we are not able to discern the cause, the idea of the teeth on the wheel.
Gist of Idea
Our sensation of green is a confused idea, like objects blurred by movement
Source
Gottfried Leibniz (New Essays on Human Understanding [1704], 4.06)
Book Reference
Leibniz,Gottfried: 'New Essays on Human Understanding', ed/tr. Remnant/Bennett [CUP 1996], p.403
A Reaction
This is one of Leibniz's less well-known objections to empiricism. He always says that intellectual ideas are capable of a clarity which is never found in sensory experience.