L O G I C. 
e'nce between object a. The univerfal formal criteria 
of Truth are therefore nothing elfe but the univerfal lo¬ 
gical marks of the agreement of Knowledge with itfelf, 
or, which is the fame, with the univerfal laws of Under- 
Handing and Reafon. 
Thefe formal Univerfal Criteria are indeed inefficient 
to objeftive tryth, but they are (till to be confidered as^ 
the conditio fine qua non of objeftive Truth. 
For, before we a(k whether Knowledge agrees with the 
objeft, we muff fir It enquire whether it agrees with itfelf 
(as to form) : and this is the bu fine Is of Logic. 
The formal Criteria of Truth in Logic are, 
i. The poftion of Contradiction,, 
7.. The poftion of Sufficient Reafon. 
By means of the former the Logical''ffqflibility , and by 
means of the latter the logical reality , of a Knowledge is 
determined. 
The logical Truth of a Knowledge requires, FirJl, that 
it be logically poffible; i. e. that it do not contradict it¬ 
felf. This mark of internal Logical Truth, is however 
only negative ; for a Knowledge which contradicts itfelf 
is certainly falfe ; but, though it do not contradict itfelf, 
it does not follow that it is true. Secondly, that it be lo¬ 
gically grounded ; i. e. that it have fufficient grounds, and 
no falfe confequences. 
This fecond criterion of external Logical Truth, or of 
the rationality of Knowledge as to grounds and confe- 
quences, is Positive. And here the following rules are 
to be obferved : 
i. From the truth of the Confequence we may infer the truth 
of the Knowledge as the ground of it, but only negatively. 
If a falfe Confequence flows from a Knowledge, then 
the Knowledge itfelf is falfe. For, if the ground were 
true, then the confequence muft alfo be true, flnee the 
confequence is determined by the ground. 
We cannot, however, infer converfely, that, becaufe no 
falfe confequences follow from a .Knowledge, it is there¬ 
fore true ; for we may draw from a falfe ground true re- 
fults. 
a. If all the Confequences of a Knowledge are true, the Know¬ 
ledge itfelf is aifo true ; for, if there were any thing falfe in 
a. knowledge, lome falfe confequences mult refult from it. 
From the confequences we may indeed infer a ground, 
but without being able to determine the ground. It is 
only from the aggregate of all the confequences that we 
can infer a determinate ground to be the true one. 
The former mode of concluding!, according to which 
the confequence can only be negatively and indirectly a 
fufficient criterion of the truth of a Knowledge, is termed 
in Logic apogogical ( modus lollens). 
This procedure, which is much ufed in Geometry, has 
this advantage, that we need only deduce one falfe con¬ 
fequence from a Knowledge to prove its falfehood. As 
for inftance, to prove that the Earth is not a plane, I 
may, without pofitive and dire ft' grounds, conclude in 
the following manner: Were the Earth a plane, the Po¬ 
lar Star would invariably be at the fame height; but this 
is not the cafe ; confequently the Earth is not a plane. 
In the pofitive and dire Cl mode of concluding, (modus 
ponens,) there is this difficulty, that the Totality of con¬ 
fequences cannot be apodiftically known. Therefore by 
this mode of concluding we can only arrive at an appa¬ 
rent or hypothetically-true, Knowledge, (Hypotkefs,) upon 
the fuppofltion, that, where many confequences'are true, 
the remainder will alfo be true. 
We are confequently here enabled to eftablilh Three 
Principles as univerfal, though merely formal or Logical 
Criteria of Truth : thefe are, 
i. The Principle of Contradiction and Identity, (principium 
centradiClionis ct identitatis,) by which the internal pojfibility 
iff a Knowledge is determined for Problematical Judgments. 
a. The Principle of Sufficient Reafon, (principium rationis 
fujfcientis,) upon which the (logical) actuality of a Know¬ 
ledge refts, namely, that it is grounded; being the mat¬ 
ter for Affertorical Judgments, 
VOL.XIII. No. , 
9 
i. The Principle of the Excluded Third, (principium exdvji 
medii into' duo conlradiCtona.) upon which the (logicai) 
neccjjily of a Knowledge is grounded ; namely, that we 
mult judge fo, and not otherwife ; i. e. that the oppofite 
is fa He ; for Apodiciical Judgments. 
The oppofite to Truth is Falfehood, which when taken 
for Truth is called Error. An erroneous judgment (for Er¬ 
ror as well as Truth occurs only in judging) is confe¬ 
quently a judgment which confounds the appearance of 
Truth with Truth itfelf. 
How Truth is pojfble ; it is eafy enough to conceive, flnee 
here the undelltar.ding aits according to the Jaws of its 
own conftitution. 
But how Error, in the formal fqnfe of the word, that is, 
how an irrational mode of thinking, is pojjible, it is difficult to 
conceive, flnee we cannot imagine how any power fiiould 
deviate from the laws of its own conftitution. We muft; 
not, therefore, look to the Underltanding and its own pro¬ 
per laws for the fource of Error, any more than to the li¬ 
mits of our Underltanding, which may indeed be the 
caufe of Ignorance, but by no means of Error. If we had 
no other power of Knowledge than t'ue pure underltand¬ 
ing, we fliould certainly never err. But, befldes Under- 
fanding, there is another indifpenfabie fource of Know¬ 
ledge; namely, Senfe, which furnilhes the materials for 
thinking, and in fo doing acts according to different laws 
from thole of the Underltanding. But from Senfe alone 
no Error can arife, becaufe Senle does not judge at all. 
The ground of all. error lies in the lecret influence of 
Senfe upon the Underltanding while it> judges, caufing it 
to mifeake fubjeCiive for objeClive grounds, and confe¬ 
quently the mere Appearance of Truth for Truth itfelf. 
What makes Error poffible is therefore this appearance. 
In one fenfe indeed we may confide! the Underltanding 
as the origin of Error, flnee for want of the requifite at¬ 
tention to the influence of Senfe it fuffers itfelf to be mif- 
led by appearance, and to take that which is true accord¬ 
ing to the laws of Senfe, as true alfo according to the laws 
of Underltanding. 
Again, Error cannot be faid to lie in our Reafon ; for this 
faculty, like every other, is endowed with its proper powers 
and limits; and therefore, cannot err. But, in judging 
of the motives of our aftions, we fuffer our Feelings to 
work upon our Reafon, and to drive it out of its courfe. 
Ignorance, indeed is occafioned by the limits of Under¬ 
ltanding, for nature has denied us much Knowledge ; but 
Error is attributable to ourfelves. One fource of Error is 
ourpronenefs to judge and decide about things which are 
without the limits of our faculties. 
All Error into which human Reafon can fall is however 
only partial. In every erroneous judgment there mult 
always be fomething true; for a complete error would be 
an entire contradiftion to the laws of Underltanding and 
Reafon. 
With refpeft to Truth and Error, it is neceflary to dif- 
tinguilh between accurate and inaccurate Knowledge. 
Knowledge is accurate when it is adequate to its objeft', 
and there is not the lealt error in it. It is inaccurate when 
there are errors in it, yet without entirely defeating its 
objeft. 
This diltinction refpefts the wider or narrower determi¬ 
nation of our knowledge; ( ccgnitio late velJlriCle determi- 
nata.) It is fometimes neceflary at firft to determine 
knowledge by very wide limits, particularly in hiftory. 
But in rational knowledge there muft he nothing vague; 
every thing muft be llriftly determined. It depends on 
the objeft of knowledge whether it ought to be determined 
vaguely or JlriCily. The wide determination leaves room 
for error, lince it is frequently miftaken for a Itrift one. 
A diftinftion may be made between Stricinefs as an ob¬ 
jective perfection of knowledge, confiltirfg in its entire agree¬ 
ment with its objeft, and Subtilty as a fubjeCiive perfection 
of knowledge! 
The knowledge of a thing is fubtile when fomething is 
discovered in it that lias been commonly overlooked, it 
D requires 
