PHILOSOPHY. 
183 
CRITIC of PURE REASON. 
INTRODUCTION. 
I. Of the Difference between Pure and Empirical 
Knowledge. 
That all our knowledge begins with experience there 
can be no doubt; for how could our knowing faculty be 
brought into play but by objefts Unking.- the fenfes, and 
partly ofthemfelves producing reprefentations,fetting the 
underftanding in motion to compare, to unite, and to fe- 
parate, and thus to work up the raw material of fenfible 
impreffions into a knowledge of objects, which we call 
experience ? We can certainly have no knowledge prior 
to experience; but it does not follow on that account 
that all our knowledge auks from experience as its fource. 
Our empirical knowledge may be a compound of what 
we receive from impreffions and of what our knowing fa¬ 
culty itfelf produces, though we may not be able to dif- 
tinguilh this addition from the original matter, until long 
experience has made us attentive to it, and qualified us 
for its reparation. 
It is a queftion, therefore, not to be decided at a glance, 
but which requires a drift inveftigation ; whether we have 
knowledge independent of experience and of the impref¬ 
fions of the fenfes ? Knowledge of this kind is termed 
d priori, and diftinguifhed from empirical or experimental 
knowledge, which has its fource a pofteriori. 
The expreffion a priori is not precife enough to deter¬ 
mine the fenfe of this queftion ; for we are accuftomed to 
lay of knowledge derived from experience, that we can 
judge of it a priori, becaufe we do not derive it imme¬ 
diately from experience, but from a univerfal rule which 
we have neverthelefs obtained from experience. Thus, 
if a man undermines the foundation of his houfe, we fay, 
he might have known it priori that it would fall, and need 
not have waited till experience convinced him that it 
really fell. This, however, he could not have known 
quite d priori ; for, that heavy bodies fall when deprived 
of their fupport he muft have previoufly learned from ex¬ 
perience. In future we lhall call that hnoivledge a priori 
which is abfolutely independent of experience. To this is 
oppofed empirical knowledge, or fuch as is only polfible d 
pofteriori; that is, by means of experience. Of know¬ 
ledge d priori, that is called pure which has nothing em¬ 
pirical in it. Thus, for inftance, the polition. Every 
change has its caufe, is a polition d priori, not however 
pure, becaufe change is a conception that can only be de¬ 
rived from experience. 
II. We are in pojfejfion of certain Knowledge d priori; and 
even Common Senfe is never without it. 
All here depends upon having a mark by which we may 
infallibly diftinguifh pure from empirical knowledge. 
Experience indeed teaches us that things are fo and fo 
conftituted, but not that they cannot be otherwife. 
Firft : If we meet with a polition that is neceffary, this is 
a judgment d priori; if, befides, it is not derived from 
any pofition which is itfelf valid as a neceffary polition, 
then it is abfolutely d priori. Secondly: Judgments of 
experience never carry with them drift, but only com¬ 
parative, univerfality (by induction); fo that, properly 
Ipeaking, we muft lay, as far as our obfervation goes, we 
have never found an exception to the rule. But, if we 
meet with a judgment that has drift univerfality, and al¬ 
lows of no exception whatever, it is not derived from ex¬ 
perience, but is abfolutely valid d priori. Empirical uni¬ 
verfality is therefore only an arbitrary extension of the 
validity of what occurs in many to that which takes 
place in all cafes; as for inftance, in the pofition, All 
bodies are heavy. If, on the other hand, drift univerfal¬ 
ity efientially belongs to a judgment, this indicates a par¬ 
ticular fource of knowledge ; that is, a faculty of know¬ 
ledge d priori. Universality and Necessity are 
therefore fure criteria of knowledge d priori, and are in- 
feparably conne&ed. As it is, however, fometimes eafier 
in praftice to Ihow the empirical limitation than the 
contingency in judgments, or to Ihow the unlimited uni¬ 
verfality of a judgment than its necejfity ; it is advifable to 
employ both thefe criterions feparately, each of which is 
in itfelf infallible. 
Nowit is eafy to (how that there are really fuch necef¬ 
fary, and in the drifted fenfe univerfal, confequently pure, 
judgments d priori, in human knowledge. As inftances 
from the Sciences, we need only produce all the propo- 
litions of the Mathematics ; and, as an inftance for Com¬ 
mon Senfe, the pofition that every change has a caufe. In 
the latter, the conception Caufe fo clearly involves that 
of the necejfity of a connexion with an EffeSl, and the 
univerfality of the rule is fo drift, that we fliould be en¬ 
tirely loft were we to derive it, as Hume did, from the 
frequent affociation of an event with that which precedes 
it; that is to fay, from an acquired habit, confequently 
from a mere J'nbjedlive neceftity of connefting reprefenta- 
tions. We could alfo (how, without thefe examples for 
proving the reality of pure principles d priori in our know¬ 
ledge, that they are indifpenfable to the poftibility of ex¬ 
perience itfelf, confequently d priori. For whence can 
experience itfelf derive its certainty, if the rules accord¬ 
ing to which it proceeds are empirical, and confequently 
contingent, and as fuch not to be conlidered as firft prin¬ 
ciples. But we may here be fatisfied with having (hovvn 
the pure ufe of our knowing faculty as a faft, together 
with its criteria. Not only fome of our judgments, but 
even fome of our conceptions, have their origin d priori. 
From the conception of a body let us abftraft all that is 
empirical, as colour, hardnefs, weight, nay even impene¬ 
trability ; (till the fpace remains which the body for¬ 
merly occupied : this cannot be annihilated. In the fame 
manner,if you omit, in the conception of any material or 
immaterial objeft, all the properties with which expe¬ 
rience has furnifhed you, yet you cannot take away from 
it that by which you conceive it to be a fubftar.ee, or an 
adherent to a fubftance, though this conception contains 
more determinations than that of an objeft in general. 
You muft be convinced, by the neceftity with which this 
conception forces itfelf upon you, that it has its feat in 
your knowing faculty d priori. 
III. Philojophy requires a Science that determines the 
Poftibility,the Principles, and the Extent, of all Knowledge 
a priori. 
Notwithftanding all that has been yet (hid, there is a fpe- 
cies of knowledge that, by means of conceptions to which 
no correfponding objefts in nature can be given, appears 
to extend the compafs of our judgments beyond the 
boundaries of all poftible experience. 
It is this very kind of knowledge that goes beyond the 
fenfible world, for which experience can furnifti neither 
guide nor correftive, and which reafon confiders far more 
important, and its final end far more fublime, than all that 
the underftanding can acquire in the field of phenomena ; 
nay,’ fo important do we confider thefe inveftigations, 
that we rather venture every thing, even at the ri(k of 
erring, than confent to relinquifti them from any ground 
of doubt, depreciation, or indifference. Thefe unavoidable 
Problems of pin re Reafon are God, Liberty, and Immor¬ 
tality. The fcience, however, whofe ultimate objeft,with 
all its preparation, is properly direfted to their folution, 
is called Metaphysics, whofe procedure is in the firft 
inftance dogmatic; that is, engages confidently in the 
accomplifhment of its objeft, without a previous invefti¬ 
gation of the ability or inability of Reafon for fo great an 
undertaking. 
It feems natural that, on forfaking the territory of ex¬ 
perience, we (hould not immediately begin to ereft an 
edifice 
