6. How is it possible to do two or three things by a single operation? It may be laid down as a general rule that each subject should be taught in combination with those which are correlative to it. Reading, penmanship, spelling, language, and nature study should work together in the acquisition and expression of ideas. As Professor Hanus[28] has pointed out, Comenius clearly foreshadowed the correlation and coördination of school studies at least two centuries before Herbart. Indeed, he went so far as to urge the correlation of school instruction with the plays and games of children. He urged that children be given tools and allowed to imitate the different handicrafts, by playing at farming, at politics, at being soldiers or architects. In the game of war they may be allowed to take the part of field-marshals, generals, captains, and standard-bearers. In that of politics they may be kings, ministers, chancellors, secretaries, and ambassadors, as well as senators, consuls, and lawyers; since such pleasantries often lead to serious things. Thus, maintains Comenius, would be fulfilled Luther’s wish that the studies of the young at school might be so organized that the pupils would take as much pleasure in them as playing at ball all day. In this way, the schools might become a real prelude to the more serious duties of practical life. _Methods of Instruction_ A correct method of instruction was to Comenius, as has already been pointed out, the panacea for most of the ills of teaching. He made reform in methodology the starting point of all his schemes for educational improvement. In the _Great didactic_ he considers reform in methods of instructing in the sciences, arts, language, morals, and religion. 1. _Science._ Knowledge of nature or science requires objects to be perceived and sufficient attention for the perception of the objects. The youth who would comprehend the sciences must observe four rules: (1) he must keep the eye of his mind pure; (2) he must see that the proper relationship is established between the eye and the object; (3) he must attend to the object; (4) he must proceed from one object to another in accordance with a suitable method.