r on; meanwhile
let us consider how, owing to our senses being limited by the
considerations of Time and Space, we are surrounded by inconceivables,
and yet it is those very inadequate conceptions which force us to
acquire Knowledge; the greatest incentive we have to pursue our
investigation is, as we have seen, the fact that Perception without
sufficient Knowledge leads us into difficulties. Let me give you two
instances of these inconceivables. Infinite Space is inconceivable by
us, but it is also quite as inconceivable, or perhaps even more so, to
think of Space being limited, and yet we are forced to declare that
one of these two must be true. Again, Matter is either composed of
ultimate bodies, of a certain size which cannot be divided, or is
infinitely divisible; both of these are inconceivable, the latter for
the same reason as that of the Infinity of Space, and the former
because it is inconceivable that the ultimate body could not be
divided into two parts by a sharp edge forced between its two sides,
or by a stronger force than at present holds it together; it has
indeed been suggested as an explanation that, if an atom could be
divided, it might cease to be matter, that its parts would have no
existence, but it is difficult to conceive how two nothings can form
one something.

Another example of Perception leading to a false Concept is our Sense
of Pain; we apply a red-hot coal to the tip of one of our fingers and
our Perception would have us believe that we feel intense pain at the
point of contact, but we know this to be a false Concept, as it can be
shown that the pain is only felt at the brain: there are in
communication with different parts of our body small microscopical
nerve threads, any of which may be severed with a pen-knife close to
the base of the skull, with the result that no pain can then be felt,
although the fingertip is just as much alive and is seen to be burning
away.

Another example is our Sense of Hearing. A musical sound is made up of
a certain number of pushes in a second, but each push is silent. It is
only, as we have seen, a musical sound to our Sense when the pushes
recur at intervals of not more than the sixteenth part of a second.
The prongs of a tuning-fork, vibrating 500 times per second, seem to
be travelling very quickly, but are really only moving at the rate of
10 inches per second, or not much over half a mile per hour, when the
amplitude is the hundredth part of an i