The meaning of "inward eye" is suggested by the other lines: when the poet is lying on his couch, alone, and begins to daydream, the daffodils become visible again in his imagination. In a sense, this is also true from a biographical point of view. In his edition of Wordsworth's major poems, Stephen Gill notes that the poem was composed in the period March 1804 – April 1807 (in other words, it is hard to date precisely) but it appears to be based on something the Wordsworths saw in April 1802. Dorothy Wordsworth's diary entry for 15 April 1802 says,
I never saw daffodils so beautiful, they grew among the stony mosses about and about them, some rested their heads on these stones, as on a pillow, for weariness and the rest tossed and reeled and danced and seemed as if they verily laughed with the wind that blew upon them over the lake, they looked so gay ever glancing and ever changing.
(In Stephen Gill's notes, there are several other examples of experiences that led to the composition of poems several years later.)
- Wordsworth, William: The Major Works, including The Prelude. Edited by Stephen Gill. [Revised edition] Oxford University Press, 2008.