Lack of intelligence, then, means a _deficiency in the organization of ideas_, a lack of those manifold interconnections by which a large number of ideas may enter into a unitary group--no matter how _effectively_ each idea is associated with a small number of others, that is, how excellent the person’s _memory_. Intelligence means organization of ideas, manifold interconnection of all those ideas which ought to enter into a unitary group, because of the natural relations of the objective facts represented by them. The discovery of a physical law in a multitude of phenomena apparently unrelated, the interpretation of an historical event of which only a few details are directly known, are examples of intelligent thought which takes into consideration innumerable experiences neglected by the less intelligent mind. Neither memory alone nor attention alone is the foundation of intelligence, but a union of memory and attention. Energy of concentration must be combined with breadth of interest. It is clear that thought determined by both these conditions is more likely to agree with the enormously complicated events in the external world than thought which is governed mainly by one of them. How does human intelligence differ from that of animals? That man is immeasurably superior to animals cannot be doubted. But human superiority does not consist in the possession of a higher faculty--let us call it reason--in no way dependent on the lower, animal faculties, to which it is added as a jeweler’s tools might be added to a blacksmith’s tools. The difference between the animal mind and the human mind is simply this: that the imaginative anticipation of possible experiences of the future is brought about in the human mind by means of more abstract and therefore more comprehensive ideas than in the animal mind. Man’s mind is by natural inheritance far more capable of forming abstract ideas than is the mind of the highest animals. Man is further immensely aided in abstract thought by language--his own invention--which furnishes him with symbols taking the place of the most complicated ideas, and because of their simplicity, effecting economy in mental work as tools and machines do in manual labor. Animals, too, possess symbols, cries; but their number is insignificant. The difference between man and animals is therefore only one of degree in properties which are common to both. But these degrees are indeed very far apart in the scale. QUESTIONS 160. How does coherent thought differ from dreaming? 161. How does coherent thought differ from mere recurrent thought? 162. What are the conditions on which coherent thought depends? 163. What is the significance of language for coherent thought? 164. What are the two sources of the idea of self? 165. What influence has language on the concept of the unity and indivisibility of self? 166. What is the true concept of the unity of mind?