he has seen
all that is visible to any other persons who have concerned themselves
with the subject. For this purpose he must endeavour to place himself at
their point of view, and strive earnestly to see the object as they see
it; nor give up the attempt until he has either added the appearance
which is floating before them to his own stock of realities, or made out
clearly that it is an optical deception.

* * * * *

The principles which we have now stated are by no means alien to common
apprehension: they are not absolutely hidden, perhaps, from any one, but
are commonly seen through a mist. We might have presented the latter
part of them in a phraseology in which they would have seemed the most
familiar of truisms: we might have cautioned inquirers against too
extensive _generalization_, and reminded them that there are _exceptions_
to all rules. Such is the current language of those who distrust
comprehensive thinking, without having any clear notion why or where it
ought to be distrusted. We have avoided the use of these expressions
purposely, because we deem them superficial and inaccurate. The error,
when there is error, does _not_ arise from generalizing too extensively;
that is, from including too wide a range of particular cases in a single
proposition. Doubtless, a man often asserts of an entire class what is
only true of a part of it; but his error generally consists not in making
too wide an assertion, but in making the wrong _kind_ of assertion: he
predicated an actual result, when he should only have predicated a
_tendency_ to that result--a power acting with a certain intensity in that
direction. With regard to _exceptions_; in any tolerably ably advanced
science there is properly no such thing as an exception. What is thought
to be an exception to a principle is always some other and distinct
principle cutting into the former: some other force which impinges against
the first force, and deflects it from its direction. There are not a _law_
and an _exception_ to that law--the law acting in ninety-nine cases, and
the exception in one. There are two laws, each possibly acting in the
whole hundred cases, and bringing about a common effect by their conjunct
operation. If the force which, being the less conspicuous of the two, is
called the disturbing force, prevails sufficiently over the other force
in some one case, to constitute that case what is commonly called an
exceptio