conceivable possibility_ that subsequent investigations will show them
to be erroneous or defective. They stand upon a foundation of Proof as
unalterable as the fiat of Fate or the decrees of the Almighty, which
can neither be shaken nor destroyed.

It is between these three Mathematical Sciences, on the one side, and
all other domains of intellectual investigation on the other, that a
line of distinct demarcation must be drawn, in any Classification of our
so-called Knowledge, in accordance with any method of classification
known to the scientific world at large. Not that the Laws or Principles
which lie at the base of all other departments of the universe are not
as stable, as definite, and as infallible as those which inhere in the
Sciences which have been specially indicated. But that, as yet, the
endeavor to apprehend fundamental Principles, in other spheres than
these, has been attended with only partial success; and hence, the
ability to establish a Mathematical or Demonstrable basis for other
regions of Thought is yet wanting, so far as is commonly known.

When, therefore, we emerge from the domains of Mathematics, Astronomy,
and Physics, we are leaving the field of _positive assurance_, of
_undeniable_ truth, and entering the realms where opinion, conjecture,
and variable degrees of certainty prevail. _The Facts of Observation may
be, indeed, as plain here as elsewhere and as firmly established. But
the conclusions drawn from them, the Scientific Principles assumed to
be established, may be erroneous or defective, and the power of
prevision, the great test of Scientific accuracy, is proportionally
wanting._ Derived, as we have hitherto seen these conclusions to be,
from Phenomena, on the supposition that a given range of Observation
will secure all the essential Principles which appertain to the _whole_
of the Phenomena included in the range, we can never be _entirely sure_