In another example previously given (page 96), the higher commander indicates only the predetermined course of action (by a directive "Capture X Island") and omits the statement of the true underlying task. The subordinate, on discovering this fact, deduces the underlying task and carries through the estimate procedure, modified, as explained for the previous example. In addition to the merits as previously stated, this method has a further advantage. The deduction of the underlying task enables the commander to judge whether any advisable or necessary deviation or departure from the predetermined course of action (page 15) involves merely a variation from the letter of his instructions or, more important, from their spirit. For instance, the directive, as in the case previously discussed, may have been "Capture X Island". The higher commander when issuing this order, may have stated his own general plan to be "This force will protect the base at A." The commander, on receipt of this directive, then deduces his true task. This is "Deny enemy bases in area ABCD" ("by capturing X Island"--a predetermined course of action), the purpose of the mission being "in order to protect the base at A". Now it may be found that the enemy, unconcerned as to X Island, is moving to reinforce Y Island and to use it as a base to attack the base at A. The commander then properly decides to capture Y Island, instead of X Island. By his identification of the predetermined course of action as such, and by his correct deduction of the true underlying task, the commander has established a sound basis for the solution of his problem. He can now, with confidence, defer or abandon the capture of X Island, and can devote his efforts to the capture of Y Island. His confidence is justified because he knows his decision to be in accordance with the spirit of his instructions. Naturally, if the higher commander directed, "This force will protect the base at A----", and added, later in his directive, "Deny enemy base sites in area ABCD by capturing X Island", the subordinate commander's deductions would have been made more easily. * * * * * The full play of the reasoning power is called for in the process of visualizing courses of action and of selecting the best. This process is the crux of the first step. Here the knowledge of the relationship between cause and effect is applied. Here, also, the commander is brought fully to realize that, to reach a sound decision, there is a requirement for a studied development of each stage by which the human mind passes from recognition of a necessity for action to the ultimate conviction as to the best course to pursue.