In the beginning was the particle
With abstract thoughts and mathematics as their language, he and a small group of physicists began to revolutionize the entire view of the material world at the beginning of the last century. Until that time, the Western world had developed an increasingly materialistic attitude towards reality. Now research in physics began to paint a new picture of material reality. Heisenberg himself formulated the emerging dichotomy of the new research in a lecture thus:
"Until now we had always believed in the old conception of Democritus, which can be paraphrased with the sentence: In the beginning was the particle (...) but perhaps there were no smallest particles at all, which can no longer be divided (...). But then what was the beginning? A law of nature, mathematics, symmetry? In the beginning there was symmetry. That sounded like Plato's philosophy in the Timaeus." 
For Democritus, the building blocks of matter were tiny particles, a small indivisible piece of invisible matter that made up the visible world. This idea was the basis of the materialistic worldview of the Western world. With the discovery of the subatomic world, this view underwent a slow transformation. New research results showed that the atom in reality does not consist of a uniform substance but is largely empty. The idea of the atom as a planetary system consisting of an atomic nucleus and the electrons orbiting around this nucleus was developed. However, it was to become apparent that the reality of this "small world" is much more puzzling and paradoxical than it appears in this conception.
Atoms are small planetary systems
The physicist and mathematician Arnold Sommerfeld saw atoms as small planetary systems. The atomic nucleus is the centre, and the electrons move in fixed orbits around this nucleus. As a young physics student, one of the young Heisenberg's first tasks was to find a mathematical expression for the electron orbits. However, Heisenberg's mathematical formulations absolutely did not fit Sommerfeld's ideas. In the calculations and later in experimental physics, the idea developed that matter has a kind of dual nature. Heisenberg's calculations led to the controversial realisation that instead of electron orbits, there are residence probabilities for electrons in the atom. The electrons themselves only come into being at the moment of observation. Albert Einstein checked Heisenberg's calculations and convinced himself of their flawlessness. Nevertheless, he could not accept the young Heisenberg's interpretation.
But even these particles, these components of the atoms, are composed of even smaller particles and could be further decomposed. And even that was not the whole reality.
New findings in the study of the nature of light and other mathematical approaches substantiated Heisenberg's assumptions. The idea of atoms as the smallest indivisible spheres of matter changed. Space and time had entered into a new relationship in Einstein's theory of relativity. According to classical Greek natural philosophy, there was a "substance" in space that was compared to water, in which changes occur continuously over time. This has now become a quantum field, which shows completely different effects than can be predicted by classical physics.
The world comes into being with observation
Thought experiments based on this, which became famous as "Schrödinger's cat", questioned the permanence of our material reality. However, these were merely thought experiments with no effect on the reality we experience every day. In working out quantum field theory, physicists came to believe that they are fields consisting of an indefinable state of pure potentiality. Quantum fields are not matter in the conventional sense, but consist of "Wirks", as the Heisenberg student Hans Peter Dürr called it. Thus, the physics of particles became a physics of interactions.
According to Heisenberg, the appearance of matter was linked to human expectation and observation. The field of potential substance forms itself into real substance according to the expectations of the observer. This is how it becomes visible in experiment, at least at the level of quantum fields. Perhaps this insight sheds a new light on the idea of the Indian philosophers who describe our world as an illusory world, as Maya.
In the world visible to us, expectation also seems to shape reality, but here with greater inertia. Buildings such as the Pyramid of Giza, which to this day is a place of pilgrimage and a secret of human activity, were already known far beyond their borders in ancient times. Its reality for humanity has something almost timeless about it. It shows that man and the matter he has shaped have been closely interwoven for a very long time and share a long-chequered history, not only in visibility but also philosophically. Cultural symbols of human activity can often unfold their effect in man and his world over thousands of years.
In the beginning was symmetry
The pre-Socratics developed their philosophies along the sensory-organic perception of nature. Their images of the structure of the world were largely derived directly from the observation of nature with the external and internal senses. The knowledge of reality that developed from this remained comprehensible to everyone who knew how to use their sense organs in an appropriate way. With Plato and his world of ideas, thinking became predominant and took its place alongside natural philosophical observation. For Plato, the foundations of matter were not small spheres, but forces. Matter was made up of the so-called Platonic bodies. He assigned four basic forces to the elements earth, water, air and fire and a Platonic basic body, a symmetry, to each of them. Fire, for example, corresponds to the pyramid and earth to the cube.
The newer physics ties in with this idea to a certain extent. It is a physics of interaction. When we observe a group of people, up to now the focus has been on the individual human being, the analysis of his or her appearance, anatomy and form. Science asked about the blueprint and "material" of the bodies. According to the "new physics", it is now rather the interaction between people that is interesting. What becomes visible through their exchange with each other and whether there is perhaps a "plan", a law that can describe the development of the interaction. This plan is then perhaps based on certain symmetries that act like laws of nature. In order to explore these interactions more closely, abstract mathematics took the place of natural philosophical observation.
With his thinking, Plato opened a door into the abstract, into areas that are closed to sensory perception. Mathematics is an instrument that seeks to make the laws of this world visible. It is able to show a person who understands its language what happens in areas that are no longer accessible to sensory-organic perception. There are mathematicians who are firmly convinced that God himself is a "mathematician".
But not all of them are convinced that this path can be followed without danger. Johann Wolfgang von Goethe opposed research with the help of mathematical abstraction, as Isaac Newton did, for example, with research with the help of sensory-organic perception. He considered the abstract path too dangerous. Werner Heisenberg was also critical of abstraction because of his intensive research on Goethe's writings. However, he had to realise that due to the historical development of science, there was no going back to Goethe's demands for mankind at this point.
The discovery of nuclear fission very quickly led to the dropping of the first two atomic bombs. Here the whole dilemma of an abstract science practised by people who do not grasp the depth of what they are doing became apparent. Heisenberg was confronted with the scientist's question of guilt.
Science in the eternal stream of knowledge
The danger of abstraction is that discoveries in science create possibilities through which humanity can destroy itself. Werner Heisenberg knew how to prevent the construction of the atomic bomb under National Socialism.
After a long discussion with his colleagues, the question of being guilty could not be conclusively settled for him. He saw science in its dynamics and history as an independent stream of development into which a scientist plunges in his time and from which he emerges again with his death.
Behind this stream of development, a truth operates as a force or potentiality, which Heisenberg hinted at in his philosophical writings at a certain point in his calculations on quantum theory:
"The energy theorem had proved valid in all of them, and so I could no longer doubt the mathematical freedom from contradiction and the coherence of the quantum mechanics it implied. At first, I was deeply frightened. I had the feeling that I was looking through the surface of atomic phenomena to a deep underlying ground of strange inner beauty, and it almost made me dizzy to think that I was now to pursue this wealth of mathematical structures that nature had spread out before me down there.” 
The mystic Jacob Böhme writes in his book Aurora oder die Morgenröte im Aufgang (Aurora or the Dawn in the Rise) that 15 minutes of looking into the spiritual background teach a person more than an entire university course of study. In such moments, man recognises those forces that hold the world together in its innermost being.
The world formula
A similar inner vision may have prompted Werner Heisenberg to work on a world formula, especially in the last years of his life. Based on Plato's idea that all matter follows mathematical laws, he looked for a way to bring relativity and quantum physics together mathematically.
This may be due to the quantum field, that primordial ground of science to which Werner Heisenberg felt committed. In it, he saw the potentiality to grow beyond this world. Such impulse perhaps culminates in the mythological dream of bringing about the dawn of a new world in which the danger of all abstraction is overcome.
Heisenberg, Werner, Gesammelte Werke, Band III: Der Teil und das Ganze, Gespräche im Umkreis der Atomphysik; Die Tendenz zur Abstraktion in der modernen Kunst und Wissenschaft (Collected Works, Volume III: The Part and the Whole, Conversations Surrounding Atomic Physics; The Tendency Towards Abstraction in Modern Art and Science), Munich 1985
 Heisenberg, Werner, Der Teil und das Ganze (The Part and the Whole), München 1969, E-Book Ausgabe, 9. Auflage 2012, p. 387 ff.
 Heisenberg, Werner, Der Teil und das Ganze (The Part and the Whole), München 1969, E-Book Ausgabe, 9. Auflage 2012, p. 183 ff.