what is called corporeal, nobody knows of its dwelling-place,
it is a fallacy and its existence an imposture.
Where is the existence, outside of mind or thought?
Western science is struggling to explain how mental states emerge from matter; and, more problematically, how a sense of self arises from matter.
Indian Advaita philosophers reverse the sequence of emergence and state that the self pre-exists everything and gives rise to mind from which the so-called material world emerges.
Blake's declaration that 'mental things alone are real' is also a reversal of the 'materialist' view. It is not necessarily Idealism; the world is real if recognised as Self, unreal if seen as other than Self (what Blake would call the Imagination).
To scientists, the self is imaginary (a simulation created by the material brain to motivate survival behaviours) To Blake the self is Imagination. (The universal Self is the Universal Imagination).
The question is: what exactly do we mean by 'matter', 'material', 'corporeal', 'real', and 'self''.
"In Blake's conception, the soul is disintegrated and must reconcile every element of her being on the road back to Eternity. This is reminiscent of the ancient Egyptian myth of the dismemberment of Osiris in the beginning of time, and man's obligation in gathering together the dismembered parts in order to arrive once more at spiritual wholeness. To do this, 'man requires a new Selfhood continually,' as Blake expressed it: 'Self annihilation' was necessary."