What is the difference between latent and manifest Orientalism in Edward Said's Orientalism?

In chapter 3 of , Said

makes the distinction between manifest Orientalism, which comprises "the various
stated
views about Oriental society, languages, literatures, history,
sociology, and so forth,"
and latent Orientalism, where Orientalist views
form an unstated background to what is actually
said. Latent Orientalism may
often be unconscious and is, by its very nature, difficult to argue
against,
which is why Said says he has concerned himself almost exclusively with
manifest
Orientalism up to this point.

However, Said
continues, it is necessary to
attack latent Orientalism because it is such a
solid and wide-ranging background to work in
numerous disciplines, including
history, economics, philosophy and politics. It is, moreover,
much less
subject to revision than manifest Orientalism:

Whatever change occurs in knowledge of the Orient is found almost exclusively
in
manifest Orientalism; the unanimity, stability, and durability of latent
Orientalism are more or
less constant.

It is latent Orientalism that underlies
imperialist and racist
ideologies, such as the notion that Europeans have a mission to civilize
the
peoples of Asia:

Thus the racial classifications
found
in Cuvier's Le Regne animal, Gobineau's
Essai sur Inegalit© des
races humaines, and Robert
Knox's The Dark Races of Man found a
willing partner in
latent Orientalism.

Said points out

that in nineteenth-century debates on imperialism, both sides accepted the premises of
latent
Orientalism, which weakened the ideological case of the
anti-imperialists. This is why it is
important to challenge latent
Orientalism, despite the obvious difficulties of doing

so.