Lactentius on the flat earth - explicit

This is one of the most explicit quotation by the Church Fathers on the flat earth.

*Chap. XXIV.---Of the Antipodes, the Heaven, and the Stars.*

How is it with those who imagine that there are antipodes opposite to
our footsteps? Do they say anything to the purpose? Or is there any one
so senseless as to believe that there are men whose footsteps are higher
than their heads? or that the things which with us are in a recumbent
position, with them hang in an inverted direction? that the crops and
trees grow downwards? that the rains, and snow, and hail fall upwards to
the earth? And does any one wonder that hanging gardens are mentioned
among the seven wonders of the world, when philosophers make hanging
fields, and seas, and cities, and mountains? The origin of this error
must also be set forth by us. For they are always deceived in the same
manner. For when they have assumed anything false in the commencement of
their investigations, led by the resemblance of the truth, they
necessarily fall into those things which are its consequences. Thus they
fall into many ridiculous things; because those things which are in
agreement with false things, must themselves be false. But since they
placed confidence in the first, they do not consider the character of
those things which follow, but defend them in every way; whereas they
ought to judge from those which follow, whether the first are true or false.

What course of argument, therefore, led them to the idea of the
antipodes? They saw the courses of the stars travelling towards the
west; they saw that the sun and the moon always set towards the same
quarter, and rise from the same. But since they did not perceive what
contrivance regulated their courses, nor how they returned from the west
to the east, but supposed that the heaven itself sloped downwards in
every direction, which appearance it must present on account of its
immense breadth, they thought that the world is round like a ball, and
they fancied that the heaven revolves in accordance with the motion of
the heavenly bodies; and thus that the stars and sun, when they have
set, by the very rapidity of the motion of the world are borne back to
the east. Therefore they both constructed brazen orbs, as though after
the figure of the world, and engraved upon them certain monstrous
images, which they said were constellations. It followed, therefore,
from this rotundity of the heaven, that the earth was enclosed in the
midst of its curved surface. But if this were so, the earth also itself
must be like a globe; for that could not possibly be anything but round,
which was held enclosed by that which was round. But if the earth also
were round, it must necessarily happen that it should present the same
appearance to all parts of the heaven; that is, that it should raise
aloft mountains, extend plains, and have level seas. And if this were
so, that last consequence also followed, that there would be no part of
the earth uninhabited by men and the other animals. Thus the rotundity
of the earth leads, in addition, to the invention of those suspended
antipodes.

But if you inquire from those who defend these marvellous fictions, why
all things do not fall into that lower part of the heaven, they reply
that such is the nature of things, that heavy bodies are borne to the
middle, and that they are all joined together towards the middle, as we
see spokes in a wheel; but that the bodies which are light, as mist,
smoke, and fire, are borne away from the middle, so as to seek the
heaven. I am at a loss what to say respecting those who, when they have
once erred, consistently persevere in their folly, and defend one vain
thing by another; but that I sometimes imagine that they either discuss
philosophy for the sake of a jest, or purposely and knowingly undertake
to defend falsehoods, as if to exercise or display their talents on
false subjects. But I should be able to prove by many arguments that it
is impossible for the heaven to be lower than the earth, were is not
that this book must now be concluded, and that some things still remain,
which are more necessary for the present work. And since it is not the
work of a single book to run over the errors of each individually, let
it be sufficient to have enumerated a few, from which the nature of the
others may be understood.