Biology Reference
In-Depth Information
The question of how the lens acquired information about the
environment was answered, in accord with the generally held 'lantern'
or 'emission' theory, by the assumption that the lens emitted some sort
of 'rays' in the form of a cone that touched objects in the outer world.
(The common observation that the eyes of animals may appear luminous
like lanterns when seen in night vision supported the theory.)
The remaining question of how individuals obtained informa-
tion about the environment from these 'rays' could be answered
in accord with the 'likeness' principle. This principle presupposed
that each object in the world could be characterized by a particular
composition of the four basic elements ('earth', 'water', 'air' and
'fire'), which the Ancient Greeks believed formed the substance
of the world, and that the 'water' element of the emitted outgoing
'rays' could gain knowledge about the 'water' elements of objects,
the 'earth' element knowledge about the 'earth' elements, and so on,
giving the individual complete knowledge of the perceived objects.
However, not all leading authorities accepted this generally
held information theory. Aristotle (384-322 BC), for instance, rejected
the 'lantern' theory on the well-known fact that humans do not see
anything in complete darkness. In contrast to the 'lantern' theory
he considered light to be an activity or a movement of an ether-
like substance originating in luminous or illuminated bodies and
transmitted through the transparent media of the environment to
the eyes.
Democritus (460-370 BC) also rejected the 'lantern' theory and
suggested that light consisted of particles that were transmitted from
the objects towards the eye. More important, he advanced the seminal
suggestion that the perception of an object and the 'real' object may
differ considerably, since both the environment between the object
and the body, and the sense organ itself, may change the messenger
particles significantly. Colour, for instance, was not considered as
part of 'real' objects, which he thought were composed of 'atoms'.
Such hypotheses and theories that deviated from the mainstream
were, however, largely ignored or treated with ridicule until as late as
Search WWH ::




Custom Search