LOGIC. 
ideas, and were to enumerate in due order all 
the simple ideas subsisting in a tiling, that 
enumeration would constitute what Is called 
a definition of the thing ; and simple ideas 
would be, as in strictness they are, unde- 
finable. But since all our sensations are 
complex, the relations of simple ideas with 
regard to each other, as residing in the same 
subject, will aiford the means of indicating 
them. Thus, light is that by which the 
organ of vision is acted upon, and the word 
is therefore defined or indicated from that 
organ. Colour is a mode of light perhaps 
too simple to be defined, but clearly indi- 
cable from any natural subject in which it 
may subsist ; as, for example, green is the 
colour of grass, red is the colour of a rose, 
and yellow the colour of an orange. 
Thus, then, the nature of terms, or words, 
is fixed by definition ; a thing for the most 
part of extreme difficulty, as, from our 
ignorance of things, and the complexity 
of the objects comprehended by usage 
under any term, it can in few cases be- 
done. The arrangement of things is by 
genera, where the same class of beings agree 
in a few attributes only; and by species, 
where they agree in more ; and tliese genera 
and species may be subordinate to each 
other in numerous pairs, the genus immedi- 
ately above each species being called tlie 
proximate genus. And from this ordinary 
arrangement logicians obtain a ready me- 
thod of defining from the specific differ- 
ence, which, though certainly much less 
adequate than those of the mathematicians, 
is nevertheless very useful. That is to say, 
the genus and the specific difference is held 
to constitute the definition of the species. 
Thus, if the words, 1. animal ; 2. four-footed ; 
3 . graminivorous ; and, 4. fleece-bearing, 
be the arrangement of certain beings pos- 
sessing life, we should define the first genus 
from the only character left by the abstrac-^ 
tion, namely, that it is a being possessing 
life ; and the first species would be ad- 
mitted to be welt defined by the words 
four-footed animal (named quadruped) ; 
the second, by the words graminivorous qua- 
druped (named cattle) ; and the third by the 
words fleece-bearing cattle (named sheep) : 
or we might less conveniently go through 
the whole series, and call the sheep a fleece- 
bearing, graminivorous, four-footed animal. 
Logicians also avail themselves in de- 
fining, where practicable, of some striking 
atti-ibute called the essence of a thing. Thus, 
under the genus, measure, the species bushel, 
peck, quartern, &c. are essentially distin- 
guished by the respective magnitudes which 
are capable of being numerically expressed. 
All our knowledge is contained in pro- 
positions, and evei-y proposition consists of 
three parts. Thus in the proposition, “ Snow 
is white,” there are three parts or terms, 
snow, which is called the subject ; is which is 
called the copula; and white, which is’called 
the predicate. If the proposition agree 
with the nature of tilings it is true, if not it 
is false. All propositions are reducible to this 
form, though both the subject and predicate 
may be expressed by many words j but the 
copula will always be .some inflexion of the 
verb to be, witli the word not if the propo- 
sition be negative. 
Propositions which contain either a plu- 
rality of predicates or' of subjects, or which 
manifest a compounded nature in either, 
have been called compound propositions. 
In the first, however, the proposition seems 
merely to be a number of propositions con- 
joined, &c.; in the latter, theform of words 
may be considered as forming a definition of 
the words or terms. Thus, “ John and 
Thomas departed,” includes the proposi- 
tions, “ John was departing, and Thomas 
was departing.” And again the proposition, 
“ Water frozen in flakes as it falls from the 
atmosphere is coloured like the powder of 
pure dry salt,” is evidently the same propo- 
sition as was first given, excepting that it 
contains a definition of the word s7iow taken 
from its formation, and of the word jvhite- 
ness from a substance of which it is one of 
the modes. 
Oiir limits will not permit us to enter into 
tile form of propositions from which they are 
denominated copulative, casual, relative, 
or di.sjunctive or modal ; as where a propo- 
sition itself becomes the subject, or posi- 
tive, or negative, and so forth. These dis- 
tinctions are in few cases useful, and in many 
tedious, trifling, and deceptive. 
Truth is determined eitlier intuitiveiy ; as 
when the relation between the predicate 
and its subject is immediately seen and ad- 
mitted. So “ the whole is equal to all its 
parts and tliese simple truths are called 
axioms : — 
Or else it is determined demonstratively; so 
the proposition, “ the opposite angles made 
by right lines crossing each other are equal,” 
is not intuitive, but requires to be demon- 
strated by a succession of axioms con- 
nected together; 
Or lastly it is determined aiialogicaily ; 
upon the probability that what has hap- 
pened will, in like Circumstances, happen 
