n sun.

It is singular how variously this question of life in other worlds has
been viewed at various stages of astronomical progress. From the time of
Pythagoras, who first, so far as is known, propounded the general theory
of the plurality of worlds, down to our own time, when Brewster and
Chalmers on the one hand, and Whewell on the other, have advocated
rival theories probably to be both set aside for a theory at once
intermediate to and more widely ranging in time and space than either,
the aspect of the subject has constantly varied, as new lights have been
thrown upon it from different directions. It may be interesting briefly
to consider what has been thought in the past on this strangely
attractive question, and then to indicate the view towards which modern
discoveries seem manifestly to point--a view not likely to undergo other
change than that resulting from clearer vision and closer approach. In
other words, I shall endeavour to show that the theory to which we are
now led by all the known facts is correct in general, though, as fresh
knowledge is obtained, it may undergo modification in details. We now
see the subject from the right point of view, though as science
progresses we may come to see it more clearly and definedly.

When men believed the earth to be a flat surface above which the heavens
were arched as a tent or canopy, they were not likely to entertain the
belief in other worlds than ours. During the earlier ages of mankind
ideas such as these prevailed. The earth had been fashioned into its
present form and condition, the heavens had been spread over it, the
sun, and moon, and stars had been set in the heavens for its use and
adornment, and there was no thought of any other world.

But while this was the general belief, there was already a school of
philosophy where another doctrine had been taught. Pythagoras had
adopted the belief of Apollonius Pergaeus that the sun is the centre of
the planetary paths, the earth one among the planets--a belief
inseparable from the doctrine of the plurality of worlds. Much argument
has been advanced to show that this belief never was adopted before the
time of Copernicus, and unquestionably it must be admitted that the
theory was not presented in the clear and simple form to which we have
become accustomed. But it is not necessary to weigh the conflicting
arguments for and against the opinion that Pythagoras and others
regarded the earth as not the fixed ce