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who is rational and modest； has ever pretended to assign the
ultimate cause of any natural operation； or to show
distinctly the action of that power； which produces any
single effect in the universe。 It is confessed； that the
utmost effort of human reason is to reduce the principles；
productive of natural phenomena； to a greater simplicity；
and to resolve the many particular effects into a few
general causes； by means of reasonings from analogy；
experience； and observation。 But as to the causes of these
general causes； we should in vain attempt their discovery；
nor shall we ever be able to satisfy ourselves； by any
particular explication of them。 These ultimate springs and
principles are totally shut up from human curiosity and
enquiry。 Elasticity； gravity； cohesion of parts；
communication of motion by impulse； these are probably the
ultimate causes and principles which we shall ever discover
in nature； and we may esteem ourselves sufficiently happy；
if； by accurate enquiry and reasoning； we can trace up the
particular phenomena to； or near to； these general
principles。 The most perfect philosophy of the natural kind
only staves off our ignorance a little longer： As perhaps
the most perfect philosophy of the moral or metaphysical
kind serves only to discover larger portions of it。 Thus the
observation of human blindness and weakness is the result of
all philosophy； and meets us at every turn； in spite of our
endeavours to elude or avoid it。
Nor is geometry； when taken into the assistance of
natural philosophy； ever able to remedy this defect； or lead
us into the knowledge of ultimate causes； by all that
accuracy of reasoning for which it is so justly celebrated。
Every part of mixed mathematics proceeds upon the
supposition that certain laws are established by nature in
her operations； and abstract reasonings are employed； either
to assist experience in the discovery of these laws； or to
determine their influence in particular instances； where it
depends upon any precise degree of distance and quantity。
Thus； it is a law of motion； discovered by experience； that
the moment or force of any body in motion is in the compound
ratio or proportion of its solid contents and its velocity；
and consequently； that a small force may remove the greatest
obstacle or raise the greatest weight； if； by any
contrivance or machinery； we can increase the velocity of
that force； so as to make it an overmatch for its
antagonist。 Geometry assists us in the application of this
law； by giving us the just dimensions of all the parts and
figures which can enter into any species of machine； but
still the discovery of the law itself is owing merely to
experience； and all the abstract reasonings in the world
could never lead us one step towards the knowledge of it。
When we reason ； and consider merely any object or
cause； as it appears to the mind； independent of all
observation； it never could suggest to us the notion of any
distinct object； such as its effect； much less； show us the
inseparable and inviolable connexion between them。 A man
must be very sagacious who could discover by reasoning that
crystal is the effect of heat； and ice of cold； without
being previously acquainted with the operation of these
qualities。
* * * *
PART II。
B/UT we have not yet attained any tolerable
satisfaction with regard to the question first proposed。
Each solution still gives rise to a new question as
difficult as the foregoing； and leads us on to farther
enquiries。 When it is asked； the proper answer
seems to be； that they are founded on the relation of cause
and effect。 When again it is asked； it may be replied in one word； E/XPERIENCE。 But
if we still carry on our sifting humour； and ask； this
implies a new question； which may be of more difficult
solution and explication。 Philosophers； that give themselves
airs of superior wisdom and sufficiency； have a hard task
when they encounter persons of inquisitive dispositions； who
push them from every corner to which they retreat； and who
are sure at last to bring them to some dangerous dilemma。
The best expedient to prevent this confusion； is to be
modest in our pretensions； and even to discover the
difficulty ourselves before it is objected to us。 By this
means； we may make a kind of merit of our very ignorance。
I shall content myself； in this section； with an easy
task； and shall pretend only to give a negative answer to
the question here proposed。 I say then； that； even after we
have experience of the operations of cause and effect； our
conclusions from that experience are not founded on
reasoning； or any process of the understanding。 This answer
we must endeavour both to explain and to defend。
It must certainly be allowed； that nature has kept us
at a great distance from all her secrets； and has afforded
us only the knowledge of a few superficial qualities of
objects； while she conceals from us those powers and
principles on which the influence of those objects entirely
depends。 Our senses inform us of the colour； weight； and
consistence of bread； but neither sense nor reason can ever
inform us of those qualities which fit it for the
nourishment and support of a human body。 Sight or feeling
conveys an idea of the actual motion of bodies； but as to
that wonderful force or power； which would carry on a moving
body for ever in a continued change of place； and which
bodies never lose but by communicating it to others； of this
we cannot form the most distant conception。 But
notwithstanding this ignorance of natural powers＇11＇ and
principles； we always presume； when we see like sensible
qualities； that they have like secret powers； and expect
that effects； similar to those which we have experienced；
will follow from them。 If a body of like colour and
consistence with that bread； which we have formerly eat； be
presented to us； we make no scruple of repeating the
experiment； and foresee； with certainty； like nourishment
and support。 Now this is a process of the mind or thought；
of which I would willingly know the foundation。 It is
allowed on all hands that there is no known connexion
between the sensible qualities and the secret powers； and
consequently； that the mind is not led to form such a
conclusion concerning their constant and regular
conjunction； by any thing which it knows of their nature。 As
to past ； it can be allowed to give and
information of those precise objects only； and
that precise period of time； which fell under its
cognizance： But why this experience should be extended to
future times； and to other objects； which for aught we know；
may be only in appearance similar； this is the main question
on which I would insist。 The bread； which I formerly eat；
nourished me； that is； a body of such sensible qualities
was； at that time； endued with such secret powers： But does
it follow； that other bread must also nourish me at another
time； and that like sensible qualities must always be
attended with like secret powers？ The consequence seems
nowise necessary。 At least； it must be acknowledged that
there is here a consequence drawn by the mind； that there is
a certain step taken； a process of thought； and an
inference； which wants to be explained。 These two
propositions are far from being the same； ； and 。
I shall allow； if you please； that the one proposition may
justly be inferred from the other： I know； in fact； that it
always is inferred。 But if you insist that the inference is
made by a chain of reasoning； I desire you to produce that
reasoning。 The connexion between these propositions is not
intuitive。 There is required a medium； which may enable the
mind to draw such an inference； if indeed it be drawn by
reasoning and argument。 What that medium is； I must confess；
passes my comprehension； and it is incumbent on those to
produce it； who assert that it really exists； and is the
origin of all our conclusions concerning matter of fact。
This negative argument must certainly； in process of
time； become altogether convincing； if many penetrating and
able philosophers shall turn their enquiries this way and no
one be ever able to discover any connecting proposition or
intermediate step； which supports the understanding in this
conclusion。 But as the question is yet new； every reader may
not trust so far to his own penetration； as to conclude；
because an argument escapes his enquiry； that therefore it
does not really exist。 For this reason it may be requisite
to venture upon a more difficult task； and enumerating all
the branches of human knowledge； endeavour to show that none
of them can a