Because of its widespread presence in Blake's more mythological works, scholars have reflected on Spectre through multiple critical approaches including Jungian archetypal analysis, as a means of mapping Blake's mythology within intellectual history and within his own biographical experience.
The mythological character of Spectre is first introduced in Blake's prophetic book Jerusalem:[6] Elsewhere in Jerusalem, Blake defines it this way: "The Spectre is the Reasoning Power in Man, and when separated from Imagination and closing itself as in steel in a Ratio of Things of Memory, It thence frames Laws and Moralities [...].
In his unpublished hand written workbook, known as the Rossetti Manuscript, he also drafted a poem that began "My Spectre around me night and day / Like a wild beast guards my way.
"[note 1] Historicist critics sometime look for direct inspirations for Blake's mythological ideas, such as Spectre, in his life experiences.
According to scholar Mark Ryan, the acclaimed literary critic Northrop Frye often aligned Spectre with persona in Jung's archetypes.