Human beings are accustomed to think of intellect as the power of having and controlling ideas and of ability to learn as synonymous with ability to have ideas. But learning by having ideas is really one of the rare and isolated events in nature.

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.

When, instead of merely associating some act with some situation in the animal way, we think the situation out, we have a set of particular feelings of its elements.

Psychology is the science of the intellects, characters and behavior of animals including man.

All that exists, exists in some amount and can be measured.

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

The dog, on the other hand, has few or no ideas because his brain acts in coarse fashion and because there are few connections with each single process.