A Class Room Logic / Deductive and Inductive, with Special Application to the Science and Art of Teaching

by George Hastings McNair

As commonly treated logic is a regulative subject. This implies the two aspects of direction and correction. Logic directs by means of the laws and forms of thought, and corrects by means of the rules of right thinking. To a certain degree both departments of logic are directive as well as corrective; but it is worthy of remark that inductive logic emphasizes the former, while deductive logic lays stress upon the latter. It is inductive logic which shows how man has acquired new knowledge; inductive logic explains the mode of procedure adopted by the discoverer and the inventor. On the other hand, deductive logic is distinctly a science of criticism. Induction directs to new truth; deduction aims to modify and correct new truth.

3. TWO TYPES OF MIND.

Though there are many special forms of thought, yet there are but two general forms; namely, induction and deduction. Inductive thought seeks the new; deductive thought corrects the old. Similarly, there are two types of mind: the inductive type and the deductive type. The former reaches out for new things, the latter is satisfied with ordering the old. In politics the man with the inductive type of mind becomes a “Liberal” or a “Progressive”;while the man with the deductive type of mind becomes a “Conservative” or a “Standpatter.” It must be conceded that both are needed in the development of the best form of Democracy. We need an unfettered freedom as advocated by Jefferson; but we also need an ordered freedom as taught by Hamilton.

4. TOO MUCH CONSERVATISM IN SCHOOL ROOM.

Since the beginning these two mental types have been in evidence—the liberal who wants to do things, and the conservative who wants to weigh things. With the liberal, it is fight whether or no; with the conservative, it is fight provided the enemy is not too formidable. The one dares; the other cautions: both are needed to balance the world.

Liberalism and conservatism may be fostered in the school room, and to maintain a true balance each must receive its share of attention. Is such the case? The passing of “district-school-individualism” and the coming of “graded-school-collectism” has transferred the emphasis from liberalism to conservatism—from the inductive type to the deductive type. In this day it seems to be more important to have the child’s work orderly, than to have it original. In the main, examination papers call for correct knowledge and not for thought; in the main, promotions are based on accuracy, not on initiative. The conservative type being in control, the schools are sending out too many “Deductives,” not enough “Inductives.” The world needs more Columbuses and Edisons.

5. THE METHOD OF THE DISCOVERER.

A change must come. The methods of instruction are too didactic and not sufficiently inspirational. Greater attention must be given to the spirit of discovery and less to the spirit of correction. The teacher must lead less and follow more; must correct less and suggest more; must tell less and direct more. If we are to give greater attention to the training of discoverers, logic may aid in this crusade by calling attention to the common mode of procedure which the discoverers of the past have adopted. This is a legitimate topic for the logician, since induction, deduction, hypothesis, and proof have ever been common tools in the discoverer’s workshop. With a view to becoming better acquainted with the common mode of procedure of the man who seeks for new truth, let us study two typical instances:

(1) The Discovery of Neptune.

The discovery of Neptune was a double one. Early in the present century it was found that Uranus was straying widely from his theoretic positions, and the cause of this deviation was for a long time unsuspected. Two astronomers, Adams in England and Leverrier in France, the former in 1843 and the latter in 1845, undertook to find out the cause of this perturbation, on the supposition of an undiscovered planet beyond Uranus. Adams reached his result first, and the English astronomers began to search for the suspected planet with their telescopes, by first making a careful map of all the stars in that part of the sky. But Leverrier, on reaching the conclusion of his search, sent his result to the Berlin observatory, where it chanced that an accurate map had just been formed of all the stars in the suspected region. On comparing this with the sky, the new planet, afterward called Neptune, was at once discovered, 23d September, 1846.