THE SUBSTITUTE; 
Or, Entomological Exchange Facilitator, and 
Entomologist’s Fire-side Companion. 
No. 5.] SATURDAY, NOVEMBER 22, 1856. [Price 2d. 
THEORY. 
There are many grades of theory. 
In Natural History we have them 
from the notion that the tail of the 
caterpillar becomes the head of the 
butterfly, up to the ‘Vestiges of 
Creation.’ The proper term for 
such things is speculation ; for we 
take it that a theory proper should 
be a deduction from facts, capable 
of explaining and being rigidly 
tested by all the circumstances 
pertaining to the subject to which 
it refers. To place a number of 
related facts together and call 
the assemblage a system is not 
enough ; the spirit of genius must 
breathe upon the dry bones, give 
them cohesion, and erect them 
into a living body. It is only 
genius can do this, but genius it- 
self fails if it be not master of 
• sufficient data ; it is then like one 
attempting to build a ship when 
he has only materials enough to 
make a raft. And if it be neces- 
- sary for him who would propound a 
theory to have a great amount of 
of knowledge as well as a large 
endowment of genius, only in a 
less degree are these qualifications 
required in those who criticise the 
work ; and when a theory is given 
to the world it behoves all to con- 
sider whether they are capable of 
understanding it, and pause ere 
they ridicule what they cannot 
comprehend. The greatest truths 
have come to light as theories ; 
and, though clear and certain 
enough to the earnest minds of 
their discoverers, have had, almost 
invariably, to fight their way 
through ridicule and persecution 
until they were established as 
truths to the apprehension of men 
in general ; the heresy of one age 
becoming the orthodoxy of the 
next. A theory which will stand 
the scrutiny of comparison with 
known facts has a great probabi- 
lity of being true, but the most 
severe test that can be applied is 
the discovery of a new fact; if it 
harmonise with the theory there 
is so much more reason to believe 
the latter to be true, but if it do 
not there is reason to believe that 
the theory is not sound. 
To discover the System of Na- 
ture is the great aim of the philo- 
sopher : every student soon learns 
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