Attention is requested here to the ease with which a decision can be made, provided one does not take into account all of the factors of a problem, or if he is not thoroughly acquainted with them; and attention is also requested to the impossibility of making a wise decision (except by chance) unless one understands all the factors, takes all into consideration, and then combines them all, assigning to each its proper weight.  From one point of view, every problem in life is like a problem in mathematics; for if all the factors are added, subtracted, multiplied, and divided correctly (that is, if they are combined correctly), and if correct values are assigned to them, the correct answer is inevitable.  In most of the problems of life, however, certainly in the problems of strategy, we do not know all of the factors, and cannot assign them their exactly proper weights; and therefore we rarely get the absolutely correct answer.  The best that any man can do is to estimate the factors as accurately as he can, judge as correctly as he can their interaction on each other, and then make his own conclusion or decision.

When a man can do this well in the ordinary affairs of life, he is said to be “a man of good judgment”; when he can do it well in a certain line of work—­say investments in real estate—­he is said to have good judgment in real estate.  The use of the word “judgment” here is excellent, because it expresses the act of a judge, who listens patiently to all the evidence in a case and then gives his decision.  And the act of the judge, and the act of any man in coming carefully to any decision, consist mainly in estimating the relative values of all the factors, and their relations to each other ("sizing them up” is the expressive slang), and then perceiving with more or less correctness what the answer is.  Some men do not have good judgment; some men highly educated, brilliant, and well-meaning, seem never to get quite the correct answer to any problem in life.  They are said to be unsuccessful and no one knows why.  Perhaps they lack that instinctive sense of proportion that some men have—­a sense as real as an “ear for music”; or perhaps they lack a willingness or a capability to think about a situation with sufficient intentness to force a clear picture of the situation with all its various features upon the mental retina.

The ability to make a mental picture, be it of a machine, of any group of material objects, such as the various units of a fleet organized as such, or of any other situation, varies with different men; but like every other kind of ability, it can be strengthened by practice, and assisted by appropriate means.  In the engineering arts, the practice is gotten by observing and remembering actual machines; and the assistance is given by drawings of different kinds.  In strategy, the practice is given by observing and remembering the movements of actual fleets; and the assistance by means of drawings of different kinds, and by war problems, and the game-board.  The game-board represents a number of successive pictures, and is not very different in principle from moving-pictures.  In fact, the suggestion has been made repeatedly for several years and is now in process of development that the various situations in tactical games might advantageously be photographed on films and afterward projected in rapid succession on a screen.