ENCYCLOPEDIA LONDINENSIS; 
OR, AN 
UNIVERSAL DICTIONARY 
OF 
ARTS, SCIENCES, and LITERATURE. 
LOGIC. 
I OG'IC, f [from >079?, Gr. difcourfe; in regard think- 
d ing is only an inward mental difcourfe, wherein the 
mind converfes with itfelf.] The art of thinking juftly; or 
of making a right ufe of our rational faculties, in defining, 
dividing, and reafoning; or, as it is defined by an excel¬ 
lent writer on this fubjeX, Logic is the art of ufing reafon 
well in our enquiries after truth, and the communication 
of it to others. Watts. 
Talk logic with acquaintance. 
And praXife rhetoric in your common talk. Shakefpcare. 
Logic is fometimes called dialeElica ; and fometimes the 
canonical art, as being a canon, or rule, for directing us 
in our reafonings. 
As, in order to think aright, it is necelfary that we 
apprehend, judge, difcourfe, and difpofe, or methodife, 
lightly ; hence perception, or apprehcnfion, judgment, dif- 
courl'e, ox reafoning, and difpofition, whence refults method, 
become the four fundamental articles of this art ; and it 
is from our reflexions on thofe operations of the mind 
that logic is, or ought to be, wholly drawn. 
Lord Bacon divides logic into four branches, according 
to the ends propofed in each ; for a man reafons, either 
to find what he leeks, or to judge of w r hat he finds, or to 
retain what he judges, or to teach what he retains; whence 
arife fo many arts of reafoning; viz. the art of inquiftion, 
or invention; the art of examining, or judgment; the art 
of preferving, or of memory; and the art of elocution , or 
delivery. 
Logic, having being extremely abufed, is now in fome 
difrepute. The fchools have fo clogged it with barbarous 
terms and plirafes, and have run it out fo much into dry 
ul'elefs fubtilties, that it feems"rather intended to exercile 
the mind in wrangling and deputation than to aftift it in 
thinking juftly. It is true, in its original it was rather 
intended as the art of cavilling than of reafoning; the 
Greeks, among whom it had its rife, being a people who 
piqued themfelves mightily upon their being able to talk 
extempore-, and to argue, by turns, on either fide of the 
queftion. Hence their dialeXici, to be always fur- 
niftied with arms for fuch rencontres, invented a fet of 
words and terms, rather than rules and reafons, fitted for 
the ufe of contention and difpute. Thus logic was only 
an art of words, which frequently had no meaning, but 
ferved rather to hide ignorance than to improve know¬ 
ledge ; to baffle reafon inftead of afflfting it; and to con¬ 
found the truth inftead of clearing it. Much of that heap 
of words, and rules, which we have borrowed from the 
old logic, is of little ufe in life; and is fo far out of the 
common ufage, that the mind does not attend to them 
without trouble; and, finding nothing in them to reward 
its attention, it foon difcharges itfelf, and lofes all idea* 
It.had conceived of them. 
VpL.JCUI. No. 88.3. 
But logic, difengaged from the jargon of the fchools,- 
and reduced into a clear and intelligible method, is the 
art of conducting the underftanding in the knowledge of 
things, and the difcovery of truth. From its proper ufe 
we gain feveral very confiderable advantages: for, 1. The 
confideration of rules incites the mind to a clofer attention 
and application in thinking; fo that we hereby become 
allured, that we make the belt ufe of our faculties. 2. 
We hereby more eafily and accurately difeover and find 
out the errors and defeXs in our reafoning; for the com¬ 
mon light of reafon, unafliited by logic, frequently obfervea 
an argumentation to be faulty, without being able to de¬ 
termine wherein the precife failure confifts. 3. By thefe 
refleXions on the order and manner of the operations of 
the mind, we are brought to a more juft and complete 
knowledge of the nature of our own underftanding. 
It is a prevalent opinion, that Ariftotle was the firft who 
inveltigated the principles of logic in a philological manner, 
and reduced it to a regular fyftem. This opinion feemt 
to receive fome countenance from his own declarations. 
“ Concerning the art of rhetoric (fays he) the ancients have 
left us numerous treatifes; but, previous to my own at¬ 
tempt, no author has ever treated of fyllogifm.” This 
afiertion, however, does not amount to any pofitive proof, 
that before his time the art of fyllogizing was unknown 
in the different fchools of philofophy eftabliflied in Greece. 
An art or fcience may be perfeXly underftood, although 
its principles have never been digeiled and arranged by 
any author. Nay, it is even certain that, before the days 
of Ariftotle, feveral feXs were aXually in poflellion of a 
regular fyltem of logic. That this fyftem received many 
important improvements from his furprifing exertions, can¬ 
not at all be doubted : yet he cannot be regarded as the 
original inventor. 
Tire fyftem of logic, however, generally aferibed to 
Ariftotle, and which was tranflated into Arabian any cen¬ 
turies,ago, conftitutes,. no doubt, at this time, the logic 
of all the nations of Alia who polfefs the Mahommedau 
faith ; yet this point had not been direXly confirmed by 
tranflalions from the oriental languages, till Mr. Balfour 
publillied, in the Afiatic Refearches for 1805, fome ex- 
traXs, with a tranflation, of the Tchzceb ul Mantik, or Ef- 
fence of Logic, an Arabic treatife of confiderable repute; 
which feem to place this queftion beyond doubt, by their 
dole coincidence in every point with the fyftem referred 
to Ariftotle. Mr. Balfour moreover endeavours to vin¬ 
dicate the Stagyrite againft the charge of lord Kaimes, 
and afiigns to him that merit which has been attributed 
to the great Bacon: “From fome of the extraXs con¬ 
tained in this paper, it will appear, i!t. That the mode of 
reafoning by induElion, illuftrated and improved by the 
great lord Verulam, in his Organum Novum, and gene¬ 
rally conftderqd as tke caufe of the rapid progrefs oi fei- 
citoe 
