Full Idea
The vulgar allow that an 'idea' implies a mind that thinks, an act of mind which we call thinking, and an object about which we think. But the philosopher conceives a fourth - the idea, which is the immediate object. …I believe this to be a mere fiction.
Gist of Idea
Only philosophers treat ideas as objects
Source
Thomas Reid (Essays on Intellectual Powers 1: Preliminary [1785], 1)
Book Reference
Reid,Thomas: 'Inquiry and Essays', ed/tr. Beanblossom /K.Lehrer [Hackett 1983], p.143
A Reaction
Another example, to add to Yablo's list, of abstract objects invented by philosophers to fill holes in their theories. This one is illuminating, because we all say 'I've got an idea'. Cf discussions of the redundancy of truth. Cf propositions.
Related Idea
Idea 8858 Philosophers keep finding unexpected objects, like models, worlds, functions, numbers, events, sets, properties [Yablo]