The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be **soluble**. It therefore becomes desirable that approximate practical methods of applying quantum mechanics should be developed, which can lead to an explanation of the main features of complex atomic systems without too much computation.

—

De la musique avant toute chose, Et pour cela préfère l'Impair Plus vague et plus **soluble** dans l'air Sans rien en lui qui pèse ou qui pose. Il faut aussi que tu n'ailles point Choisir tes mots sans quelque méprise: Rien de plus cher que la chanson grise Où l'Indécis au Précis se joint.

— Let's hear the music first and foremost,

And that means no more one-two-one-twos…

Something more vague instead, something lighter

Dissolving in air, weightless as air.

When you choose your words, no need to search

In strict dictionaries for pinpoint

Definitions. Better the subtle

And heady Songs of Imprecision.

Line 1; Sorrell p. 123.

If politics is the art of the possible, research is surely the art of the **soluble**. Both are immensely practical-minded affairs.

— Review of Arthur Koestler’s

The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be **soluble**. It therefore becomes desirable that approximate practical methods of applying quantum mechanics should be developed, which can lead to an explanation of the main features of complex atomic systems without too much computation.

— Paul Dirac (1926)