in two dimensions; but most commonly he intends to signify tangible
distance in the third dimension. And it is in this sense that he
employs "distance" as the equivalent of "space." Distance in two
dimensions is, for Berkeley, not space, but extension. By taking a
pencil and interpolating the words "visible" and "tangible" before
"distance" wherever the context renders them necessary, Berkeley's
statements may be made perfectly consistent; though he has not always
extricated himself from the entanglement caused by his own loose
phraseology, which rises to a climax in the last ten sections of
the "Theory of Vision," in which he endeavours to prove that a pure
intelligence able to see, but devoid of the sense of touch, could have
no idea of a plane figure. Thus he says in section 156:--

"All that is properly perceived by the visual faculty amounts
to no more than colours with their variations and different
proportions of light and shade; but the perpetual mutability
and fleetingness of those immediate objects of sight
render them incapable of being managed after the manner of
geometrical figures, nor is it in any degree useful that they
should. It is true there be divers of them perceived at once,
and more of some and less of others; but accurately to compute
their magnitude, and assign precise determinate proportions
between things so variable and inconstant, if we suppose
it possible to be done, must yet be a very trifling and
insignificant labour."

If, by this, Berkeley means that by vision alone, a straight line
cannot be distinguished from a curved one, a circle from a square,
a long line from a short one, a large angle from a small one, his
position is surely absurd in itself and contradictory to his own