What are the metaphors in Emerson's quote, "this thought which is called I is the mould into which the world is poured?"
There was an interesting philosophical discussion going on in Emerson's time about the way we "learn" about or apprehend the world. Locke and others had posited that everything we learn comes through our sense; there can, therefore, be no "knowledge" about things that are not perceived. Kant and other "Transcendental" thinkers [difficult to define this group, but we'll use the term in it's generally accepted sense] argued that we have internal mechanisms that make understanding what the sense take in understandable, that order things according to, for example, time and space. The world is not just "out there" --- it is poured into the "I" --- so I can learn things not just from sensory experience, but through immediate perceptions of some truths. Emerson uses the language of "tuition" for the learning that comes through work and the senses, and "intuition" which comes through this more immediate perception. This is part of the reason that Emerson is able to derive such meaning from nature, and it part of the reason the Romantic poets in England turned from rationalism to a more immediate perception of the world through nature.