Science, Theory and Practice. 169 
To mention some familiar instances, the improved form of the 
plow-share, the drill culture, the turnip culture, as practised in 
England, these were so many theories in the minds of those who 
first proposed and practised them; is it not even self evident, that 
every item of practice must have existed in the form of theory, 
consciously or unconsciously, of the man, no matter how long ago, 
who first introduced it? A shrewd guess, is but another name for 
an unconscious theory. 
Theory has got a bad name, from two causes, and science, 
though a confusion of terms, has shared it. 
First, a theory, in first hands, seldom prospers; for the inventor 
is usually more fond of his discovery, than of the main chance. 
Jethro Tull was a great discoverer, but he was not a successful 
farmer. 
Secondly, so called theories, based on assumed principles, or 
imperfect observations, have brought the word into disrepute; it 
is only when a theoretic mind is based in science, or corrected by 
practice, that its conclusions are of value. 
The above remarks may serve as an introduction to the follow- 
ing extracts from the article " Theory," in the Penny Cyclopedia, 
from which I am sure many of your readers will derive pleasure 
and encouragement. 
"Before coming to the distinction between theory and practice 
we must observe that theories may be divided into two classes, 
the more perfect and the less perfect. We cannot say that any 
theory is absolutely perfect, but there are some of which the de- 
fects are hardly perceptible, and others in which the contrary is the 
case "********** 
*' In such a subject, our theory instead of being an all sufficient 
guide, is only a help, the services of which are to be used to an ex- 
tent which discrimination derived from practice and experience, 
must point out. Many a person, who thinks he is proceeding upon 
experience only, is really making use of a mixture in which there 
is theory, though his own knowledge of the process he uses, and of 
its history, may not be sufficient to inform him of it." 
" A person who uses an imperfect theory, with the confidence 
due only to a perfect one, will naturally fall into an abundance of 
mistakes; his predictions will be crossed by disturbing circum- 
stances of which his theory is not able to take account, and his 
credit will be lowered by the failure. And inasmuch as more 
theories are imperfect than perfect, and of those who attend to any 
thing, the number of those who acquire very sound habits of judg- 
ing, is very small compared with that of those who do not get so 
far, it must have happened, as it has happened, that a great 
quantity of mistakes has been made by those who do not under- 
stand the true use of an imperfect theory. Hence much discredit 
has been thrown upon theory in general, and the schism of the- 
