218 PHILOSOPHY OF ZOOLOGY. 
of rhyme, puns, colloquial phrases, and alliteration. In 
many cases, however, ideas return in the mind without any 
exertion to recall them. In some instances we can trace 
back the process by which they were introduced, while, in 
others, we have no notion of their origin or connection. If 
the process is known, we perceive that it has been excited 
by some impression of resemblance. 
Some confusion has arisen with regard to our notions of 
Memory, from the introduction of the term conception. 
This phrase, m numerous instances, refers to the original 
image or impression produced on the mind, through the 
medium of the senses, thus using it as synonimous with 
sensation and perception ; while in others, it is applied to 
the combining efforts of the imagimation, or the simple re- 
collective exertions of the memory. 
When an idea returns to the mind either spontaneously 
or by an effort of recollection, we employ the faculty of at- 
tention in examining its condition. We either view it as a 
whole, in relation to the whole or the parts of other objects, 
or we attend to the qualities of its particular parts in refe- 
rence to one another, or to the whole, or the parts of some 
other cbject. This selective act of attention some have 
considered as a separate power, under the denomimation of 
abstraction. But as we have seen attention practising ab- 
straction, in regard to the operations of the senses, and as 
it acts in a similar manner with the ideas of recollection, we 
see no necessity for regarding this operation of the mind 
as a distinct faculty. Indeed it must appear obvious, up- 
on a little consideration, that the terms abstraction, exa- 
mination and comparison, merely express the single or 
combined acts of the attention and memory. 
Ideas are excited by the memory in general, with a fa- 
cility proportional to the degree of attention originally be- 
stowed on the impressions, their intensity, and the frequency 
