Interdisciplinary conferences are now commonplace. This inter-
disciplinary exchange between two outstanding scientists, how-
ever, occurring in 1935, was highly unusual, perhaps unique. Sir
Arthur Eddington was well known to the reading public through
such books as The Nature of the Physical World ( 1929). Koffka, one
of the three founders of Gestalt psychology, had just published
The Principles of Gestalt Psychology ( 1935), a book which was the
first comprehensive text and exposition of the Gestalt theory.

For Koffka, the Gestalt concept, however, was much more than
a new movement or a new school in psychology. It was an ap-
proach to life, a belief, a new gate opening on stalemated prob-
lems. Stimulated by Eddington New Pathways in Science, just off
the press, Koffka's impulse was to share with him the possible Ge-
stalt implications in such areas as the materialistic-dualistic di-
lemma, the principle of uncertainty, entropy, and other major the-
oretical concepts which Eddington had discussed.

The idea to write a personal letter to Eddington required some
reenforcement, for Koffka was by nature modest about his own
contributions. Here are the steps in his correspondence in 1935.

[KK] I finished Eddington's book yesterday. . . . a grand book,
much more difficult than The Nature of the Physical World, and
not the solution as I see it, in however vague a form. But a

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