needs be, in a fashion, seen.

Now as stated above (A. 4), it is impossible that one and the same
thing should be believed and seen by the same person. Hence it is
equally impossible for one and the same thing to be an object of
science and of belief for the same person. It may happen, however,
that a thing which is an object of vision or science for one, is
believed by another: since we hope to see some day what we now
believe about the Trinity, according to 1 Cor. 13:12: "We see now
through a glass in a dark manner; but then face to face": which
vision the angels possess already; so that what we believe, they see.
In like manner it may happen that what is an object of vision or
scientific knowledge for one man, even in the state of a wayfarer,
is, for another man, an object of faith, because he does not know it
by demonstration.

Nevertheless that which is proposed to be believed equally by all, is
equally unknown by all as an object of science: such are the things
which are of faith simply. Consequently faith and science are not
about the same things.

Reply Obj. 1: Unbelievers are in ignorance of things that are of
faith, for neither do they see or know them in themselves, nor do
they know them to be credible. The faithful, on the other hand, know
them, not as by demonstration, but by the light of faith which makes
them see that they ought to believe them, as stated above (A. 4, ad
2, 3).

Reply Obj. 2: The reasons employed by holy men to prove things that
are of faith, are not demonstrations; they are either persuasive