448 THE PENN MONTHLY. [June, 
The field of the known is very limited, as compared with that of 
the unknown, in the experience of the Amoeba. In its first move- 
ments, it has absolutely no basis on which to establish an anticipa- 
tion of the future. Such is also the situation of the young of 
every animal. But the cases of the inferior and superior species 
present the important difference, that in the former there are few 
or no mental powers derived by inheritance, while in the latter 
such exist in proportion to the position of the species in the scale 
of intelligence. 
The facts of evolution teach that the habits of animals have 
been modified during past geological ages, under the influence of 
changes in their physical surroundings. While these changes may 
perhaps, have furnished the stimuli to the adoption of new habits, 
the conditions have not often been so rigid as to define exactly 
what those habits should be, in some or all of their details. The 
animal has necessarily proceeded blindly in many instances; in 
others, his mental darkness has been illumined by a low grade of 
imagination. This may be believed in view of the many attempts 
which animals often make before succeeding in attaining a desired 
end. Imagination plays an important part in the origin of motives 
and of actions, and is related to predication. It is defined as the 
presentation or construction of images or representations from 
items of experience, which representations so far differ in the con- 
nection of their details from actual experience, or so far lack the 
qualities of experiences, as not to constitute a predication of future 
events. Predication may be defined as the certain knowledge of 
the unexperienced from the experienced; while imagination in- 
cludes the grades of probable, possible, and impossible concepts, 
constructed from the same material as predication. Whether this 
faculty exists in the animals which cannot speak, is not readily 
ascertained ; but, inasmuch as many of them predicate, it is proba- 
ble that they possess some degree of imagination also. But it is 
obviously a quality of the highest types of mind, since its devel- 
opment depends primarily on the furniture of memory, derived 
from a long period of experience, whose amount depends on recep- 
tivity and retentiveness. 
VI. THE ORIGIN OF MOTIVES. 
It has been said that the operation ordinarily called choosing, in» 
which the will is popularly supposed to be free, consists merely of 
a sum in addition and subtraction, where various inducements are 
