Full Idea
It is obvious that green comes from a mixture of blue and yellow; which makes it credible that the idea of green is composed of the ideas of those two colours, although the idea of green appears to us as simple as that of blue.
Gist of Idea
The idea of green seems simple, but it must be compounded of the ideas of blue and yellow
Source
Gottfried Leibniz (New Essays on Human Understanding [1704], 2.07)
Book Reference
Leibniz,Gottfried: 'New Essays on Human Understanding', ed/tr. Remnant/Bennett [CUP 1996], p.120
A Reaction
This shows the use of 'idea' at that time for non-verbal mental events and concepts. Ideas are not, then, just undestood as phenomena, but can be analysed and explained more deeply.