I think that there is a moral to this story, namely that it is more important to have beauty in one's equations that to have them fit experiment. If Schrödinger had been more confident of his work, he could have published it some months earlier, and he could have published a more accurate equation. It seems that if one is working from the point of view of getting beauty in one's equations, and if one has really a sound insight, one is on a sure line of progress. If there is not complete agreement between the results of one's work and experiment, one should not allow oneself to be too discouraged, because the discrepancy may well be due to minor features that are not properly taken into account and that will get cleared up with further development of the theory.

Mathematics is the tool specially suited for dealing with abstract concepts of any kind and there is no limit to its power in this field.

Preface to *The principles of Quantum Mechanics* (Oxford, 1930)

In science one tries to tell people, in such a way as to be understood by everyone, something that no one ever knew before. But in poetry, it's the exact opposite.

Quoted in H Eves *Mathematical Circles Adieu* (Boston 1977).

I learned to distrust all physical concepts as the basis for a theory. Instead one should put one's trust in a mathematical scheme, even if the scheme does not appear at first sight to be connected with physics. One should concentrate on getting interesting mathematics.

Now when Heisenberg noticed that, he was really scared.

Quoted in D MacHale, *Comic Sections * (Dublin 1993)

I consider that I understand an equation when I can predict the properties of its solutions, without actually solving it.

Quoted in F Wilczek, B Devine, *Longing for the Harmonies*

This result is too beautiful to be false; it is more important to have beauty in one's equations than to have them fit experiment.

The evolution of the Physicist's Picture of Nature *Scientific American* **208** (5) (1963)

If one is working from the point of view of getting beauty into one's equation, ... one is on a sure line of progress.

The evolution of the Physicist's Picture of Nature *Scientific American* **208** (5) (1963)

The steady progress of physics requires for its theoretical formulation a mathematics which get continually more advanced. This is only natural and to be expected. What however was not expected by the scientific workers of the last century was the particular form that the line of advancement of mathematics would take, namely it was expected that mathematics would get more and more complicated, but would rest on a permanent basis of axioms and definitions, while actually the modern physical developments have required a mathematics that continually shifts its foundation and gets more abstract. Non-euclidean geometry and noncommutative algebra, which were at one time were considered to be purely fictions of the mind and pastimes of logical thinkers, have now been found to be very necessary for the description of general facts of the physical world. It seems likely that this process of increasing abstraction will continue in the future and the advance in physics is to be associated with continual modification and generalisation of the axioms at the base of mathematics rather than with a logical development of any one mathematical scheme on a fixed foundation.

Paper on Magnetic Monopoles (1931)

God used beautiful mathematics in creating the world.