Locke’s Theory of Perception 253
all perception on the analogy of contact experience. If the
external body is neither directly nor indirectly in contact
with the sense-organ, there is no perception; and if the mind
is not in some sense in contact with the stimulated sense-
organ, as when in sleep or death it is “retired from the
senses,” then again there is no perception. The mind per-
ceives physical objects only when, from their side, they send
representatives of themselves to where the sense-organ is,
and when, from its side, the mind extends itself to be in some
way or other where that sense-organ is. Then there is
contact—and experience. There is no such thing as percep-
tion at a distance. What the mind directly perceives must
be immediately in the mind, that is, where the mind is.
But when of an evening I look out on Jupiter, is not the
bright orb that I see really millions of miles away from my
observant self and identical with the real Jupiter? This
could hardly be the case, since as we well know the real
Jupiter could suddenly cease to exist and still the duped ob-
server would go on seeing his own little yellow luminary
for more than half an hour. Locke knew of his Danish
contemporary Romer, and of his discovery of the finite
velocity of light, made by observations of the satellites of
Jupiter. On this basis he criticized the opinion of Paul
Malebranche that an object millions of leagues away is per-
ceived the moment it is uncovered or begins to emit light.1
This argument, from the space-time interval between the
perceiver and the external event causing his perception, is
perhaps the best available one when it comes to proving that
what you apprehend in sensation is when and where the sensa-
tion occurs, not when and where the remote external object
is. It is the argument that certain modern epistemologists
rely on most to establish such a dualistic theory of perception
1 Wks. loc. cit.