1 0 8 D O C . 2 8 I N D U C T I O N A N D D E D U C T I O N

28. “Induction and Deduction in Physics”

[Einstein 1919g]

Published 25 December 1919

In: Berliner Tageblatt, 25 December 1919, p. [1] of 4. Beiblatt.

The most simple picture one can form about the creation of an empirical science is

along the lines of an inductive method. Individual facts are selected and grouped

together such that their lawful connection becomes clearly apparent. By grouping

these laws together, one can achieve other more general laws until a more or less

uniform system for the available individual facts has been established—such how-

ever, that the intellect, looking backwards, could arrive at the individual facts re-

versely in a merely mental way.

However, a merely casual look at factual development already teaches us that

big advances in scientific knowledge originated this way only to a small degree.

For if a researcher would approach things without a preconceived opinion, how

would he be able to pick the facts from the tremendous richness of the most com-

plicated experiences that are simple enough to reveal their connections through

laws? Galileo would never have found the law of free-fall without the precon-

ceived opinion that the situations as we find them are complicated by the effects of

air resistance, and therefore, that one has to focus on cases where this effect has

only negligible influence.

The truly great advances in our understanding of nature originated in a man-

ner almost diametrically opposed to induction. The intuitive grasp of the essentials

or a large complex of facts leads the scientist to the postulation of a hypothetical

basic law, or several such basic laws. From the basic law (system of axioms) he

derives his conclusion as completely as possible in a purely logically deductive

manner. These conclusions, derived from the basic law (and often only after time-

consuming developments and calculations), can then be compared to experience,

and in this manner provide criteria for the justification of the assumed basic law.

Basic law (axioms) and conclusions together form what is called a “theory.” Every

expert knows that the greatest advances in natural science, e.g., Newton’s theory

of gravitation, thermodynamics, the kinetic theory of gases, modern electrody-

namics, etc. all originated in this manner, and that their basis has this, in principal,

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