ide the "gloomy dean" of St. Paul's,
whether through well-considered thought or through the psychological
shock of the Great War, have come to look upon this rash, unmitigated
enthusiasm about the earth's future as a fool's paradise. At any rate,
no treatment of the idea of progress would be complete which did not
dwell upon the limitations to that idea, now definitely obvious to
thoughtful men.

As early as 1879, in Saporta's "Le Monde des Plantes," we run upon one
serious setback to unqualified expectations of progress. Men began to
take into account the fact that this earth is not a permanent affair.
"We recognize from this point of view as from others," wrote Saporta,
"that the world was once young; then adolescent; that it has even passed
the age of maturity; man has come late, when a beginning of physical
decadence had struck the globe, his domain." [12] Here is a fact to give
enthusiasm over earthly progress serious pause. This earth, once
uninhabitable, will be uninhabitable again. If not by wholesale
catastrophe, then by the slow wearing down of the sun's heat, already
passed its climacteric, this planet, the transient theatre of the human
drama, will be no longer the scene of man's activity, but as cold as the
moon, or as hot as colliding stars in heaven, will be able to sustain
human life no more. "The grandest material works of the human race,"
wrote Faye in 1884, "will have to be effaced by degrees under the action
of a few physical forces which will survive man for a time. Nothing will
remain, not even the ruins." [13]

Every suggested clew to a possible escape from the grimness of the
planet's dissolution has been followed up with careful search. The
discovery of radioactivity seemed to promise endlessly extended life to
our sun, but Sir E. Rutherford, before the Royal Astronomical Society,
has roundly denied that the discovery materially lengthens our estimate
of the sun's tenure of life and has said that if the sun were made of
uranium it would not because of that last five years the longer as a
giver of heat.[14] Whether we will or not, we have no choice except to
face the tremendous fact, calmly set down by von Hartmann in 1904: "The
only question is whether . . . the world-process will work itself out
slowly in prodigious lapse of time, according to purely physical laws; or
whether it will find its end by means of some metaphysical resource when
it has reached its culminating point. Only i