For origin and development of human faculty we must look to these processes of association in lower animals.

To the intelligent man with an interest in human nature it must often appear strange that so much of the energy of the scientific world has been spent on the study of the body and so little on the study of the mind.

This growth in the number, speed of formation, permanence, delicacy and complexity of associations possible for an animal reaches its acme in the case of man.

The real difference between a man's scientific judgments about himself and the judgment of others about him is he has added sources of knowledge.

Psychology helps to measure the probability that an aim is attainable.

From the lowest animals of which we can affirm intelligence up to man this type of intellect is found.

Nowhere more truly than in his mental capacities is man a part of nature.