I 
UNDERSTANDING. 
mathematical propositions arc, in some cases, 
attended with a practical assent, in the pro- 
per sense of these words ; as when a per- 
son takes this or that method of executing 
a projected design, in consequence of some 
mathematical proposition assented to from 
his own examination, or from the authority 
of others. Now the train of voluntary 
actions denoting the practical assent, is 
produced by the frequent recurrency of 
ideas of utility and importance. These ope- 
rate by association, and tliough tlie ra- 
tional assent be a previous requisite, yet 
the degree of the practical assent is propor- 
tional to the vividness of those ideas ; and 
in most cases they strengthen the rational 
assent by reaction. 
II. Propositions concerning natural bo- 
dies are of two kinds, vulgar and scienti- 
iical. Of the first kind are, “milk is white,” 
“ gold is yellow,” “ a dog barks,” &c. These 
are evidently nothing more than forming the 
terras denoting the whole or some com- 
ponent parts of the complex idea, into a 
proposition, or employing those denoting 
some of its common adjuncts in the same 
way. The assent given to such propositions 
arises from the associations of the terms as 
well as of the ideas denoted by them. 
. In scientifical propositions concerning 
natural bodies, a definition having been 
made of the body from its properties, 
another property or power is joined to them 
as a constant or common associate. Thus 
gold is said to be soluble in the nitro-mn- 
riatic acid. Now to persons who have 
made the proper experiments a sufficient 
number of times, these words suggest the 
ideas which occur in those experiments, 
and conversely are suggested by them, in 
the same manner as the vulgar propositions 
above-mentioned suggest, and are suggested 
by common appearances. But then, if 
they be scientific persons, their readiness to 
affirm that gold is soluble in this acid uni- 
versally, arises also from the experiments of 
others, and from theif own and other per- 
sons’ observations on tlie constancy and 
tenor of nature. They find it to be a ge- 
neral truth, that almost any two or three re- 
markable qualities of a natural body, infer 
the rest, being never found without them ; 
and hence arises a readiness to affirm re- 
specting all bodies possessing those two or 
three leading qualities, whatever may be 
affirmed of one. 
The propositions formed respecting na- 
tural bodies are often attended with a high 
degree of practical assent, arising chiefly 
from some supposed utility and importance, 
and which is no ways proportioned to the 
foregoing or similar acknowledged causes of 
rational assent. And in some cases the 
practical assent takes place before the rati- 
onal ; but then, after some time, the rati- 
onal assent is generated and cemented most 
firmly by the prevalence of the practical. 
This prodess is particularly observable in 
the regards paid to medicines; that is, in 
the rational and practical assent to the pro- 
positions concerning their virtues. 
The , influence of the practical assent 
over the rational, arises from their being 
united in so many cases. And the vivid- 
ness of the ideas arising from the supposed 
utility, importance, &c. produce a more 
ready and closer union of the terms of tlie 
proposition. 
III. The evidences for past facts are a 
man’s owm memory, and the authority of 
others. These are under proper restric- 
tions, the usual associates of true past facts, 
and therefore produce the readiness to 
affirm a past fact to be true, that is, the 
rational assent. The integrity and compe- 
tency of tlie witnesses being the principal 
restriction or requisite in the accounts of 
past facts, become principal associates to 
tile assent to them ; and the contrary quali- 
ties to dissent. 
If it be asked ‘ how a narration of an event 
supposed to be certainly true, or to be doubt- 
ful, or to be entirely fictitious, differs in its 
effect upon the mind in these circumstances 
respectively, the words in which it is nar- 
rated being the same in case?’ it may be 
replied, first, in having the terms true, 
doubtful, or fictitious, with a variety of 
ideas usually associated with them, and the 
corresponding internal feelings of respect, 
anxiety, dislike, &c. connected with them 
respectively j whence the whole effects, 
exerted by each upon the mind, will differ 
considerably from one another. Secondly, 
if the events be of a very interesting nature, 
the related ideas will recur oftener, and 
thus agitate the mind the more, in propor- 
tion to the supposed truth of the event. 
And it confirms this, that the frequent 
recurrence to the mind of an interesting 
event, supposed to be doubtful, or even 
fictitious, by degrees makes it appear like 
a real one. The practical assent to past 
facts often produces the rational assent, as 
in the other cases before spoken of. 
IV. The evidence for future tacts is of 
the #ame kind with that for the propositions 
concerning natural bodies, being like it ta- 
