^ f. UBBARV - JScholarship - Johns Hopkins University

VISION 27
air into definite visible forms {airoTvirma-n) is the peculiar
characteristic of Democritus theory of vision. He held that
if there were pure vacuum, and not air, around us, the
emanations or images sent from the visible objects would
reach the eye unblurred: that is to say, they would then
report the exact form of an object, no matter how great the
distance from which they might come. ' Democritus,' says
Aristotle\ 'is not correct in his view that, if the space
between object and eye were pure void, an ant could be
seen clearly in the sky.' As it is, however, the air takes
the first copy of the object, and the eye receives it only
at second hand, while the likeness of this copy to the
original becomes more and more imperfect in proportion
to the distance it has to travel.
§ 14. Theophrastus" criticizes these tenets of Demo- Theocritus:
' His notion of modelling (airoTvirooa-is) in air is „itid^s
quite absurd. Whatever is capable of being moulded into Demoshape
must have density, and must not be liable to dis- theory of
persion; this he implies when he illustrates the process, vision.
and compares it with the stamping of impressions on wax.
In the next place, such modelling might take place more
successfully in water than in air, water being more dense;
hence we should see better in water. As a fact, however,
we see worse. In the third place, why should one who
(as Democritus in his treatise irfpl db&v does) bdieves in
the emanation of the shape of an object ^, hold this further
belief in the modelling of the air ? For the actual images
{eibwka avTÖ.) of the objects are represented in the eye,
according to the former belief. But, again, if we grant that,
as Democritus says, the air is moulded into shape, being like
wax impressed and Condensed, how does the reflexion of ai>
image take place, and of what nature is it ? If there is really
such an image, i.e. an Impression taken by the air from the
object seen, it must be, in this as in other instances.on the side
facing the latter. Such being the case, the image cannot come
opposite to the eye unless the moulded portion of air is first
^ 419* 15. ^ Be Sens. §§ 51 seqq. (Diels, Box., pp. 513-15).
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