A man decides to walk one mile from A to B. A god waits
in readiness to throw up a wall blocking the man’s further
advance when the man has traveled ½ mile. A second god
(unknown to the first) waits in readiness to throw up a
wall of his own blocking the man’s further advance when
the man has traveled ¼ mile. A third god . . . & c. ad
infinitum. It is clear that this infinite sequence of mere
intentions (assuming the contrary to fact conditional that
each god would succeed in executing his intentions if
given the opportunity) logically entails . . . that the man
will be arrested at point A; he will not be able to pass
beyond it, even though not a single wall will in fact be
thrown down in his path.