####
I received an early copy of Heisenberg's first work a little before publication
and I studied it for a while and within a week or two
I saw that the noncommutation was really the dominant characteristic of
Heisenberg's new theory.
It was really more important than Heisenberg's idea of
building up the theory in terms of quantities closely
connected with experimental results.
So I was led to concentrate on the idea of noncommutation
and to see how the ordinary dynamics which people had been using
until then should be modified to include it.

---P. A. M. Dirac

```
```*The Development of Quantum Theory
(J. Robert Oppenheimer Memorial Prize Acceptance Speech)*,
Gordon and Breach Publishers, New York, 1971, pp. 20-24.

The quote used an an epigraph on p. 2 in *Operator Commutation Relations*
by Palle E. T. Jorgensen and Robert T. Moore, D. Reidel, Dordrecht / Boston / Lancaster, 1984,
is an abridgement of the above passage.

A longer excerpt (with the curious substitution of "commutation" for "noncommutation" where it first appears)
is presented as an epigraph in the announcement of a
Program on Noncommutative Algebra
at the
Mathematical Sciences Research Institute.

Back when I thought about what to put into
*Operator Commutation Relations*, I relied a lot on
*The Historical Development of Quantum Theory*
by Jagdish Mehra and Helmut Rechenberg,
Springer-Verlag, New York, 1982-- .
I was also impressed by how well researched this lovely
book-set is. The two authors, Mehra and Rechenberg, did long interviews over the span
of time when they worked on their book set. They had known Bohr, and they
had many meetings with Heisenberg, Pauli, Dirac, and many more, and as I
remember, much material in the book set results directly from these
interviews. It is good that the two co-authors had the interviews, as these
giants in quantum theory passed on shortly after the book-set was completed.
I think the book set is a treasure of information on quantum theory
(especially the mathematical part of it) and on the architects of the
theory.

Late in life, Dirac would always tell the physicists at conferences
to look to the *math* for clues to the deep questions in physics, and he
liked to use his (Dirac) equation for the electron as an example, stressing
that he was led to it by paying attention to the beauty of the math, more
than to the physics experiments. He was alive when I was working on
*Operator Commutation Relations*, and I talked to
him a few times. He told me that he was happy to be quoted. He used to
visit his son Gabriel Dirac (graph theory) who was my colleague in Aarhus.

Some interesting links for Dirac:

Dirac
[in the
MacTutor History of Mathematics archive
at the University of St Andrews]

Quotations by Dirac
[in the same
archive]

The Nobel Prize in Physics 1933

Roundy interviews Professor Dirac

to
Quotes selected by Palle Jorgensen