commonly still diffident in their determinations: and if any of the
learned be inclined, from their natural temper, to haughtiness and
obstinacy, a small tincture of Pyrrhonism might abate their pride,
by showing them, that the few advantages, which they may have attained
over their fellows, are but inconsiderable, if compared with the
universal perplexity and confusion, which is inherent in human nature.
In general, there is a degree of doubt, and caution, and modesty,
which, in all kinds of scrutiny and decision, ought for ever to
accompany a just reasoner.

  130. Another species of mitigated scepticism which may be of
advantage to mankind, and which may be the natural result of the
Pyrrhonian doubts and scruples, is the limitation of our enquiries
to such subjects as are best adapted to the narrow capacity of human
understanding. The imagination of man is naturally sublime,
delighted with whatever is remote and extraordinary, and running,
without control, into the most distant parts of space and time in
order to avoid the objects, which custom has rendered too familiar
to it. A correct Judgement observes a contrary method, and avoiding
all distant and high enquiries, confines itself to common life, and to
such subjects as fall under daily practice and experience; leaving the
more sublime topics to the embellishment of poets and orators, or to
the arts of priests and politicians. To bring us to so salutary a
determination, nothing can be more serviceable, than to be once
thoroughly convinced of the force of the Pyrrhonian doubt, and of
the impossibility, that anything, but the strong power of natural
instinct, could free us from it. Those who have a propensity to
philosophy, will still continue their researches; because they
reflect, that, besides the immediate pleasure, attending such an
occupation, philosophical decisions are nothing but the reflections of
common life, methodized and corrected. But they will never be
tempted to go beyond common life, so long as they consider the
imperfection of those faculties which they employ, their narrow reach,
and their inaccurate operations. While we cannot give a satisfactory
reason, why we believe, after a thousand experiments, that a stone
will fall, or fire burn; can we ever satisfy ourselves concerning
any determination, which we may form, with regard to the origin of
worlds, and the situation of nature, from, and to eternity?

  This narrow limitation, indeed, of our enquiries, is, in every
respect, so reasonable, that it suffices to make the slightest
examination into the natural powers of the human mind and to compare
them with their objects, in order to recommend it to us. We shall then
find what are the proper subjects of science and enquiry.

  131. It seems to me, that the only objects of the abstract science
or of demonstration are quantity and number, and that all attempts
to extend this more perfect species of knowledge beyond these bounds
are mere sophistry and illusion. As the component parts of quantity
and number are entirely similar, their relations become intricate
and involved; and nothing can be more curious, as well as useful, than
to trace, by a variety of mediums, their equality or inequality,
through their different appearances. But as all other ideas are
clearly distinct and different from each other, we can never advance
farther, by our utmost scrutiny, than to observe this diversity,
and, by an obvious reflection, pronounce one thing not to be
another. Or if there be any difficulty in these decisions, it proceeds
entirely from the undeterminate meaning of words, which is corrected
by juster definitions. That the square of the hypothenuse is equal
to the squares of the other two sides, cannot be known, let the
terms be ever so exactly defined, without a train of reasoning and
enquiry. But to convince us of this proposition, that where there is
no property, there can be no injustice, it is only necessary to define
the terms, and explain injustice to be a violation of property. This
proposition is, indeed, nothing but a more imperfect definition. It is
the same case with all those pretended syllogistical reasonings, which
may be found in every other branch of learning, except the sciences of
quantity and number; and these may safely, I think, be pronounced
the only proper objects of knowledge and demonstration.

  132. All other enquiries of men regard only matter of fact and
existence; and these are evidently incapable of demonstration.
Whatever is may not be. No negation of a fact can involve a
contradiction. The non-existence of any being, without exception, is
as clear and distinct an idea as its existence. The proposition, which
affirms it not to be, however false, is no less conceivable and
intelligible, than that which affirms it to be. The case is
different with the sciences, properly so called. Every proposition,
which is not true, is there confused and unintelligible. That the cube
root of 64 is equal to the half of 10, is a false proposition, and can
never be distinctly conceived. But that Caesar, or the angel
Gabriel, or any being never existed, may be a false proposition, but
still is perfectly conceivable, and implies no contradiction.

  The existence, therefore, of any being can only be proved by
arguments from its cause or its effect; and these arguments are
founded entirely on experience. If we reason a priori, anything may
appear able to produce anything. The falling of a pebble may, for
aught we know, extinguish the sun; or the wish of a man control the
planets in their orbits. It is only experience, which teaches us the
nature and bounds of cause and effect, and enables us to infer the
existence of one object from that of another.* Such is the
foundation of moral reasoning, which forms the greater part of human
knowledge, and is the source of all human action and behaviour.

  * That impious maxim of the ancient philosophy, Ex nihilo, nihil
fit, by which the creation of matter was excluded, ceases to be a
maxim, according to this philosophy. Not only the will of the
supreme Being may create matter; but, for aught we know a priori,
the will of any other being might create it, or any other cause,