Beauty is ever to the lonely mind a shadow fleeting she is never plain. She is a visitor who leaves behind the gift of grief, the souvenir of pain.

The lines cast beauty as something apprehended most intensely by an isolated or inward-looking consciousness—an experience that is vivid but unstable (“a shadow fleeting”). Beauty is not “plain” or fully graspable; it arrives as a visitation rather than a possession. The paradox is that aesthetic rapture carries an aftertaste of loss: once the moment passes, what remains is longing, grief, and the pain of transience. The quote thus links beauty to impermanence and to the lonely mind’s heightened sensitivity, suggesting that the very capacity to perceive beauty deeply also exposes one to sorrow when it inevitably departs.