erion and the proof are thrown into the 117
_circulus in probando_, by which it is found that they are both
of them untrustworthy, for as each looks for proof from the
other, each is as untrustworthy as the other. Since then one
cannot prefer one idea to another, either without a proof and a
criterion or with them, the ideas that differ according to
different conditions cannot be judged, so that the suspension of
judgment in regard to the nature of external objects follows
through this Trope also.

THE FIFTH TROPE.

The fifth Trope is that based upon position, distance, and 118
place, for, according to each of these, the same things appear
different, as for example, the same arcade seen from either end
appears curtailed, but from the middle it looks symmetrical on
every side; and the same ship appears small and motionless from
afar, and large and in motion near by, and the same tower
appears round from a distance, but square near by. So much for
distance. Now in reference to place, we say that the light 119
of the lamp appears dim in the sun, but bright in the dark; and
the same rudder appears broken in the sea, but straight out of
it; and the egg in the bird is soft, but in the air hard; and
the lyngurion is a fluid in the lynx, but is hard in the air;
and the coral is soft in the sea, but hard in the air; and a
tone of voice appears different produced by a syrinx, and by a
flute, and different simply in the air. Also in reference to 120
position, the same picture leaned back appears smooth, and
leaned forward a little seems to have hollows and protuberances,
and the necks of doves appear different in color according to
the difference in inclination. Since then all phenomena are 121
seen in relation to place, distance, and position, each of which
relation makes a great difference with the idea, as we have
mentioned, we shall be obliged by this Trope also to come to the
suspension of judgment. For he who wishes to give preference to
certain ones of these ideas will attempt the impossible. For if 122
he simply makes the decision without proof he will be
untrustworthy. If, however, he wishes to make use of a proof,
should he say that the proof is false, he contradicts himself,
but if he declares the proof to be true, proof of its proof will
be demanded of him, and another proof for that, which proof also
must be true, and so on to the _regressus in infinitum_. It is
impossible