1804. ] 
acknowledge, that to be relieved from it 
by rational conviction, is in the highe(t 
degree defirable. The only real queition 
then is, Whether, in the prefent {tate of hu- 
man knowledge, there are many branches 
of {cience in which the certainty of truth 
is attainable? and, as a corollary, Whe- 
ther, in caf-s where we cannot be certain 
of our principles, it be not preferable to 
have before our eyes the poflibility of 
miltake, than to proceed with entire con- 
fidence ? 
Sciences may be divided into the pure 
and the mixed: in the former, the funda 
mental principles being fufceptible of ab- 
folute demontiration, the reafoner is only 
requiced to take care that his deductions 
are ftricily logical, in order to be cer- 
tain of his concluiions. In the latter, 
the principles being only probabilities, or, 
at leaft, a mixture of certainties and pro- 
babilities, the conclufions can only be pro- 
bable. Of the firft clafs there aie, per- 
haps, no other than thofe termed by fo- 
reigners the exact feiences, or, fuch as are 
founded upon mathematical demontftra- 
tion. Poffioly, metaphyfical fpeculations 
would, to a certain degree, be entitled to 
the fame honour, were men agreed in the 
ufe of fundamental terms. To the fe- 
cond clafs are referable allithofe which 
derive their rules from experience, or 
from a number of facts generalized ; in 
which cafes, as there are always either 
faéts to be adduced of an oppofite nature, 
oran imperfeét analogy in the application, 
nothing can be obtained but a prepon- 
derancy of probability. This, indeed, 
may be fufficient to a&t upon, when aéting 
as neceffary, but it cannot, except in a 
very fanguine temper, exclude doubt. 
It will not be cenied by any one ac- 
quainted with the hiftory of medicine, 
that no {fcience has laboured under a 
greater multiplicity of theories, contra- 
dictory to each other and to themf{elves ; 
infomuch, that praétitioners of a certain 
fianding are generally found to defert all 
theory, and fettle in an empiricifm directed 
only by experience, or obvious analogies, 
Woerethisis not the cafe, but the diétates of 
the {chool continue to govern the opinions 
and practice of the graduate, it mutt be 
extremely lucky for himfelf and his pa- 
tients if he has happened to imbibe the 
only true theory ; for it will be allowed, 
that a talfe one muft be much worfe than 
none at all. [f he goes on, without doubt 
or hefitation, to put in force the rules of 
his art, he may indeed practife ¢* con{ci- 
any and comfortably,” but it will 
depend upon the folidi-y of thofe rules, 
whether ‘he becomes a benefit or a 
puifance to focicty. Dr, Reid, I pre- 
Scepticifm and Dogmatifm in Science compared. 
97 
fume, would not jbefitate to pronounce 
that a difciple of Galen, Sylvius, Stahl, 
or Boerhaave, adhering pertinacioufly to 
the doctrines of his malter, would pro- 
bably be an inftrument of great mifchief ; 
and he would agree, that to fuch an one, 
an infufion of {ce pticifm would be a very 
falutary reftraint. The ‘ decifion,”’ there- 
fore, which he means to recommend, mutt 
proceed upon the fuppofition that the per- 
fon poffetiing it, is certainly and infaili- 
bly in the right. That he conceives him- 
feif to be in that predicament, 1s rendered 
evident by his fublequent monthly com- 
munication, in which, alluding to the 
Brunonian theory, he affirms, that “no 
one can fail to adopt the radical doétrine 
of it, who. is capable of under@anding 
it 5°’ which doétrine he further reprefents 
aS. €x raétly analogous to the Newtonian 
principle of gravitation. ‘Thus fortunate 
in haves “* fylua im tanta,’ iound the 
true golden bough, he may confdently 
trult in its guidance ; nor do I mean in 
pay place to call in queftion the grounds 
t his confidence. 
Bot to revert to the proper fubject of 
my letter. Although it be true that (cep- 
ticifm does betray a defect of knowledge, 
or an obfeurity of concept ion, I cannot 
but be of opinion, thatit is fafer than dog. 
matifm in ali matters of pra€tice, where 
the principles are fill undeterminate, and 
where various and oppofite notions are 
held with nearly equal plaufbility. Such 
are almoft all queltions relative to civil 
and_ political regulation, the right deci- 
ae of which can only be the refult of 
epeated trial and accurate inveltigation. 
To fet out in thele cafes with the affur mp- 
tion of difputed principles, and with a 
refolution to adhere to them in the face 
of mifcarriages and failures, is furely to 
put the welfare of mankind to an unwar- 
rantable hazard. Where, indeed, it is 
neceflary to choofe one of two things, and 
abide by the choice, a firm decifion is 
preferable to wavering irrefolution; but 
where the object is gradually to dilcover 
the beit fyftem in any cafe, there can be 
no doubt that it will be done moft effec- 
tually by thofe who, fitting loofe to pre- 
conceived theories, patiently work their 
way to truth, not ferupling to recal theic 
fteps when they fufpet they have been 
mifled, and perpetually aware of the pof- 
fibility of error. “This, if is true, is a 
flow procefs, nor is it fure at the laft ta. 
lead to certainty ; but it always leayes an 
opening for correction and improvement. 
In the {cience of legiflation, (which, being 
a matter entirely under human manage- 
ment, might feem capable of reduction to 
fixed principles,) how often do we fee an 
apparently 
