80. An observation of the phenomena of the imagination will confirm what we have explained by the mere order of intelligence. When I imagine the extension of an orange, I imagine it with a limit, with this or that color, and with these or those qualities; since it is not possible for me to imagine a figure without lines which terminate it. This limit in the imagination is distinct both from the extension which it encloses, and from the extension which it excludes. If it were not so distinguished, we could not imagine it as limit, and it would not answer its object, which is to enable us to distinguish that which it encloses. Therefore, the abstraction is not complete. In the imagination there is always something determinate, which is the limit or the lines which constitute the limit. Destroy these limits, and the imagination expands, until it becomes lost in a sort of dark, unbounded abyss, such as we imagine beyond the universe.
A very simple example will make this explanation clearer. Our imagination may be compared to a black board on which a figure is marked with chalk. When we see the white line on the board which forms the figure, we see the figure also; but if we rub out the line, there remains only the uniform figure of the board. If we suppose the lines which terminate the black board to be indefinitely withdrawn, we shall look in vain for a figure; we see only a black surface indefinitely extended. There is a sufficient parity between this and the manner in which the imagination pictures to itself an endless space.
81. The idea of an abstract extension which is limited, is a contradiction. Limit takes from extension generality; and generality destroys the limit. There can, therefore, be no abstract idea of limited extension; but when we form an idea of extension in the abstract, we conceive it as unlimited, and the imagination attempting to follow the understanding, pictures to itself an indefinite space.
82. Summing up this doctrine, and deducing its inevitable consequences, we may say:
I. That space is nothing else than the extension of bodies.
II. That the idea of space is the idea of extension.
III. That the different parts conceived in space are the ideas of particular extensions, from which we have not taken their limits.
IV. That the idea of infinite space is the idea of extension in general, abstracted from all limit.
V. That indefinite space arises necessarily from the imagination, which destroys the limit in attempting to follow the generalizing march of the understanding.
VI. That where there is no body there is no space.