PREFACE 
make against the growing tendency to humanize 
the lower animals. The paper was widely read and 
discussed, and bore fruit in many ways, much of 
it good and wholesome fruit, but a little of it bitter 
and acrid. For obvious reasons that paper is not 
included in this collection. But I have given all the 
essays that were the outcome of the currents of 
thought and inquiry that it set going in my mind, 
and I have given them nearly in the order in which 
they were written, so that the reader may see the 
growth of my own mind and opinions in relation to 
the subject. I confess I have not been fully able to 
persuade myself that the lower animals ever show 
anything more than a faint gleam of what we call 
thought and reflection, —the power to evolve ideas 
from sense impressions, — except feebly in the case 
of the dog and the apes, and possibly the elephant. 
Nearly all the anima] behavior that the credulous 
public looks upon as the outcome of reason is simply 
the result of the adaptiveness and plasticity of 
instinct. The animal has impulses and impressions 
where we have ideas and concepts. Of our faculties 
I concede to them perception, sense memory, and 
association of memories, and little else. Without 
these it would be impossible for their lives to go on. 
I am aware that there is much repetition in this 
volume, and that the names of several of the separate 
chapters differ much more than do the subjects 
discussed in them. 
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