[1] It is not only the inferior powers of the soul which this
plague of sin has seized, but the contagion has ascended
into the higher regions of the soul. The most supreme, most
spiritual faculty in man's mind, the understanding power of
man, is corrupted, and needs renewing. To a carnal
understanding not enlightened by the Word, this always has
been and is the greatest paradox. Indeed, when blind
reason, which thinks it sees, is judge, it is not strange
that this corruption of the understanding should be a
wonder to it. The reason, being the supreme faculty of all
the rest, which judges all else, and is judged by none but
itself, because of its nearness to itself, it least
discerns itself. As a man's eye, though it may see the
deformity of another member, yet not the bloodshot that is
in itself, but it must have a glass by which to discern it.
And so, though even corrupt nature discerns the rebellions
of the affections and sensual part of man by its own light,
as the heathens did, and complained thereof, yet it cannot
discern the infection and defilement that is in the spirit
itself, but the glass of the Word is the first that
discovers it; and when that glass is also brought, there
had need by an inward light of grace, which is opposite to
this corruption, to discover it.--_T. Goodwin,_ 1600-1679.