Definition.com
An Idea (n.) has two lives: as an act of my mind it can be no greater than I am; as the thing it represents it may exceed me entirely.
Definition.com
An Idea (n.) cannot, by itself, be false: I truly imagine a chimera just as I truly imagine a goat.
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An Idea (n.) that comes involuntarily need not come from outside: I may have some power, not well known to myself, that makes ideas without external objects — as in sleep.
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An Idea (n.) needs a cause as real as what it pictures: even the idea of a stone needs a cause containing as much reality as the stone.
Definition.com
An Idea (n.) is a picture that may fall short of its original but can never contain anything greater.