The principle of unicity explains that each event, each living being, each object, each person or each circumstance has the characteristic of its
uniqueness
Uniqueness is a state or condition wherein someone or something is unlike anything else in comparison, or is remarkable, or unusual. When used in relation to humans, it is often in relation to a person's personality, or some specific characterist ...
, of its particularity. Other similar events, living beings, objects, persons or circumstances may exist, but never the same entity.
The theory of
quantum mechanics
Quantum mechanics is the fundamental physical Scientific theory, theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms. Reprinted, Addison-Wesley, 1989, It is ...
(QM) suggests that the ''principle of unicity'' is invalid. In other words, no physical system, physical process, or object has a ''unique'' and ''complete'' description. Instead, QM, the most successfully tested and proven theoretical framework, stipulates that all physical reality can be described in multiple
alternative, incompatible ways, using independent descriptions that cannot be contrasted, compared, or combined.
The principle of unicity implies that every conceivable property of a particular physical system will be either ''true'' or ''false'', as observable experiments can either confirm or reject the property, as implied by the unique and exhaustive property description assumption. In effect, unicity implies the existence of a ''universal truth functional'', which is incompatible with a quantum
Hilbert space
In mathematics, a Hilbert space is a real number, real or complex number, complex inner product space that is also a complete metric space with respect to the metric induced by the inner product. It generalizes the notion of Euclidean space. The ...
of dimension greater than two, in particular
Minkowski spacetime
In physics, Minkowski space (or Minkowski spacetime) () is the main mathematical description of spacetime in the absence of gravitation. It combines inertial space and time manifolds into a four-dimensional model.
The model helps show how a s ...
is four dimensional space. Therefore, unicity is not part of quantum reality. For each physical object, the intrinsic incompatibility of its (stochastic) quantum descriptions prevents them from being combined into a more precise (deterministic) descriptions, which makes it impossible to create a unique and exhaustive description.
References
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Uniqueness