This finds further support in what Descartes says, for example, in the First Replies: "…the idea of the sun is the sun itself existing in the intellect — not of course formally existing, as it does in the heavens, but objectively existing, i.e., in the way in which objects normally are in the intellect" (AT VII 102 3; CSM II 75).
Is an idea "of" the sun insofar as the sun is the object at which the act-idea is directed, or is the idea "of" the sun insofar as the sun is the object exhibited in the idea's content?
So, in the case of the sensory idea of the sun, the idea can be understood to be directed at the sun, that is, at the sun itself, the object in the heavens.
Here's his explanation: "When I say, 'the sun is the cause of day,' I do not mean that my idea of the sun causes or excites in me the idea of day; but that the physical object, the sun itself, is the cause from which the outward phenomenon, day, follows as an effect.
Thus Mill, for example, wrote, "When I say, 'the sun is the cause of the day,' I do not mean that my idea of the sun causes or excites in me the idea of day".
The idea of the sun is arguably like the idea of Pegasus in that there is no formal-sun.
"Everyone likes the idea of the sun going dark in the middle of the day.
Mrs. Szundy came up with the idea of midnight sun glacier hikes three years ago.
I had a vague, romantic idea of the sun setting over a log cabin perched on the downs within sight of Stonehenge.
