The Personal World

The personal world is by no means a new idea. Interpretations of this nature appeared in the 1970s. A world of this nature is the solution to fundamental problems in quantum theory. With this understanding, the physics work perfectly. But for a hundred years it has not been possible to puzzle out how it works, given the ordinary world we know about. The resolution is that quantum theory is the physics of two different types of world. And this is why the meaning has been impenetrable. The personal world exists as well as the ordinary world.

This is what emerges when the ontology of this type of world is explained, how it comes to exist. The basis of this explanation is explored in this section of the site.

The Relative World

It is fundamental to quantum theory that there are two competing descriptions of the real physical world. Physicist Lev Vaidman, a specialist in the foundations of quantum mechanics, puts clear definitions to the two types. The first is the ordinary world, as we generally understand it:

A world is the totality of macroscopic objects: stars, cities, people, grains of sand, etc. in a definite classically described state. (2008)

In other words, ordinary real stuff. This is the concept of the world we are all used to. This is called the ‘classical’ view. The other type of world is the personal world, which he calls the ‘relative world’:

“In this world, all objects which the sentient being perceives have definite states, but objects that are not under her observation might be in a superposition of different (classical) states. (2008)

In other words, objects not observed are ‘indeterminate’, unreal. It is called the relative world because the world is only defined relative to the individual.

It is well established in modern physics that certain facts are relative to the individual. This is the central principle in special relativity. Position and velocity exist only relative to the observer. But as described in this article in the Guardian by Carlo Rovelli, it seems that all facts are relative. He is the author of ‘Relational Quantum Mechanics’, described in detail here at the Stanford Encyclopedia of Philosophy. This is the nature of the personal world.

Many Worlds

The resolution arises in the context of Hugh Everett’s famous many-worlds interpretation of quantum theory, The ‘Relative State’ Formulation of Quantum Mechanics. He demonstrates that the great paradox of quantum theory, the ‘measurement problem’, is resolved if all possible worlds exist. His discovery dates from 1957, and half a century later this is increasingly accepted. David Deutsch, a renowned physicist who works on fundamental issues, states this is without question correct:

The point that theorists tend to miss is that the multiplicity of reality is not only, or even primarily, a consequence of quantum theory. It is quite simply an observed fact. (1996)


One of the direct implications of the many worlds is that there are a great many copies of a specific individual in the many worlds. This is described by cosmologist Max Tegmark in his paper Parallel Universes (2003). Given this, the new idea is very simple.

The many worlds all exist in the same place at the same time, superposed. This is fundamental to quantum theory. This would seem to mean that all the ‘copies’ are just one individual. As we shall see, this is true for the mind though it is not the case for the body.

With respect to the mind, this means that there is only one of this individual. And this individual is present in all those worlds all at once. In this case, from the subjective perspective of this individual, the world is the superposed sum of all of them. And this automatically has the properties of a relative world. This is the ontology of the personal world.

The personal world is something completely different to the ordinary world. It is a whole class of worlds, superposed, here called a ‘superworld’. This is a very different type of world, and this is why it has very different properties to the ordinary world. As will be described further on it is a different ‘logical type’.


The superposition principle is fundamental to all physics. A common example is the way waves superimpose, and the result is the sum of the different waves. This image on the Wikipedia page illustrates the idea very nicely.

Waves on water are superposed
Waves on water are superposed

The principle simply means that when systems are superposed, the resulting system operates like the sum of those systems. This applies even to solid physical systems. This is because at the quantum level, all physical reality is defined by a wave of probability, the ‘wave function’.

This means that when physical states are superposed, it works just like the waves on the water. The result is that the real objects are added together, just like multiple slides on an overhead projector. This is illustrated with the images of the butterfly below. The last image is the superposed sum of all the possible wing positions. In this superposition, only the body of the butterfly is the same in all the images, so only the body is solid and definite. The wings are the superposed sum of all the possible variations, so the image of the wings is indefinite.

Superposition of different wing positions
Superposition of different wing positions

The Superworld

The same principle applies to the superposition of worlds. All the objects and events that the individual perceives are the same in all the worlds. So when these worlds are superposed, all these objects are determinate, real and solid, like the body of the butterfly. But for everything else, everything that has not been observed, the opposite is true. Every possible variation of how things could be is included in the superposition. So all the things unobserved are indeterminate, like the wings of the butterfly.

In other words, the result is literally the superposition of different (classical) states, just as Vaidman describes. This is the ontology of the relative world, meaning this is what it is ‘made of’. This is the nature of the superworld.

It is not quite as simple as that which is why this idea has not surfaced before. The full explanation is given in the next section, The World Hologram.