MN and the Principia

Paul A. Nelson (
Fri, 27 Mar 1998 10:32:29 -0600 (CST)

Wayne R. Belcher wrote:

>I was rectnly purusing the ASA archives and in a recent posting you stated
>that Newton's _Principia_ does not speak of MN. I would disagree. Consider
>the following quote from Book 3 (Rules of Reasoning and Philosophy):
>"We are to admit no more causes of natural things than such as are both true
>and sufficient to explain their appearance; therefore to the same natural
>effects we must, as far as possible, assing the same causes."
>This seems to be a pretty clear indication of MN to me.

Not to me.

Notice that Newton says "to the same natural effects we must...assign
the same causes." The adjective "natural" occurs before "effects," but
NOT before "causes" -- which is consistent with the rest of the _Principia_:

This most beautiful system of the sun, planets, and comets,
could only proceed from the counsel and dominion of an
intelligent and powerful Being. And if the fixed stars are the
centres of other like systems, these, being formed by the
like wise counsel, must be all subject to the dominion of
One; especially since the light of the fixed stars is of the
same nature with the light of the sun, and from every system
light passes into all other systems: and lest the systems of
the fixed stars should, by their gravity, fall on each other, he
hath placed those systems at immense distances from each
other. (General Scholium)

Newton's argument here has the following form:

1. Our local solar system could only have been intelligently

2. If there are other such systems, then [by Rule II -- to the
same effects assign the same causes], they, too, are

3. This is confirmed by the unitary nature of the light of the
fixed stars when compared with the light of the sun.

Thus Newton's own application of Rule II leads him to infer
intelligent design elsewhere in the universe.

Newton consistently assigned the *origin* of the solar system to
intelligent design and stressed this to his contemporaries. Roger
Cotes, for instance, in his Preface to the second edition of the
_Principia_, commented:

Without all doubt this world, so diversified with that
variety of forms and motions we find in it, could arise
from nothing but the perfectly free will of God directing
and presiding over all....All sound and true philosophy
is founded on the appearances of things; and if these
phenomena draw us, against our wills, to such principles
as most clearly manifest to us the most excellent
counsel and supreme dominion of the All-wise and
Almighty Being, they are not therefore to be laid aside
because some men may perhaps dislike them. These
men may call them miracles or occult qualities, but names
maliciously given ought not to be a disadvantage to the
things themselves, unless these men will say at last
that all philosophy ought to be founded in atheism.

I can still remember reading this passage years ago as a first-year
graduate student, and thinking, "That's it -- that is methodological
naturalism captured in a single phrase: 'All philosophy [meaning
"science" for Newton and his contemporaries] ought to be founded
in atheism." Well, if not in "atheism," exactly, in the wide pretense
that if God exists, he acts undectectably only through natural causes
-- which for Will Provine, Eugenie Scott, and the other philosophical
naturalists reading this, is very nearly as good as the real thing
(atheism, that is).

Here is the MN formulation of Newton's Rule II:

Therefore to the same natural effects we must, as far as possible,
assign the same natural causes.

Newton didn't say that, and he didn't believe it either.

Paul Nelson