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

Amongst the minds of animals that of man leads, not as a demigod from another planet, but as a king from the same race.

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

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.

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.

The intellectual evolution of the race consists in an increase in the number, delicacy, complexity, permanence and speed of formation of such associations.

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.