Article May 8, 1920 ISSUE

"Quod Erat Demonstrandum"

JAMES L. BRUCE

Early in their study of geometry students meet with the words "quod erat demonstrandum." It becomes more familiar to them in its abbreviated form Q. E. D., which they soon learn to repeat glibly and with a sense of satisfaction, for it marks the completion of their task, meaning as it does, "which was to be proved." Mathematics has furnished numberless helpful illustrations to the student of Christian Science, and in this branch called geometry, with its necessary steps from the statement of a proposition to be proved to the final Q. E. D., there may be found many valuable lessons.

The author of the mathematical textbook has gathered the propositions from various sources, for some of them are hundreds or even thousands of years old, and has stated them not as suppositions but as facts. To the teacher they are facts, and it is to the student alone that they may seem anything else. To him they may seem so many words until he has proved them, but he only is affected by his conclusions regarding them. The mathematical world does not stand aside eagerly awaiting his decisions. It already knows the truth of the propositions. It also knows that the conclusions the student may reach have no effect on the subject one way or the other. What the student does prove is, however, of tremendous importance to himself: even whether or not he shall have a share in the benefit which comes from a knowledge of the subject.

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