TRUTH is within ourselves;  it takes no rise
From outward things, whate’er you may believe.
There is an inmost center in us all,
Where truth abides in fullness; and around,
Wall upon wall, the gross flesh hems it in,
This perfect, clear perception – which is truth.
A baffling and perverting carnal mesh
Binds it, and makes all error:  and, to KNOW,
Rather consists in opening out a way
Whence the imprisoned splendour may escape,
Than in effecting entry for a light
Supposed to be without.

-- From “Paracelsus” by Robert Browning