[Sidenote: Conception of Energy]

29.

Impetus is the impression of motion conveyed by the motive power to the
object moved. Every {152} impression tends to permanence or seeks to
attain permanence. That every impression seeks after permanence is
proved by the impression made by the sun on the eye which regards it,
and in the impression of sound made by the hammer which strikes a bell.
Every impression seeks after permanence, as is shown in the image of
impetus communicated to the object moved.

30.

A weight seeks to fall to the centre of the earth by the most direct
way.

[Sidenote: In Praise of the Sun]

31.

If you look at the stars, warding off the rays (as may be done by
looking through a small hole made by the extreme point of a fine needle
placed so as almost to touch the eye), they will appear so small as to
seem as though nothing could be smaller; it is owing to their great
distance that they appear so small, for many of them are very many
times larger than the star which is the earth with its water. Now
reflect what appearance this our star must have from so great a
distance, and then consider how many stars might be placed--both in
longitude and latitude--between those stars which are sown in the dark
space. I can never refrain from blaming many of the ancients who said
that the size of the sun was no greater than {153} it appears; among
whom was Epicurus. I believe he founded his reasoning on a light
placed in our atmosphere equidistant from the centre of the earth,
which, to any one looking at it, never appears to diminish in size from
whatever distance it is seen.

32.

I shall reserve the reasons of its size and power for later. But I
greatly marvel that Socrates should have depreciated such a body, and
that he should have said that it resembled an incandescent stone; and
he who opposed him as regards this error acted rightly. But I wish I
had words to blame those who seek to exalt the worship of men more than
that of the sun, since in the universe there is no body of greater
magnitude and power to be seen than the sun. And its light illumines
all the celestial bodies which are distributed throughout the universe;
and the vital spark descends from it, because the heat which is in
living beings comes from the soul, and there is no other centre of heat
and light in the universe, as will be shown later; and it is certain
that those who have elected to worship men as gods--as Jup