In part 1 of this article we discussed the role of the observer in determining the outcome of measurement or observation, which was the main point of the quoted Platos statement. We also mentioned how the mathematical formulation of quantum physics presented some serious difficulty in as much as it came up with results that seemed absurd. A well-known example is the paradox known as Schrodingers cat.

Edwin Schrodinger along with Werner Heisenberg was the main architect of quantum mechanics. In 1935 he devised a thought experiment to illustrate the ambiguity associated with the state of a system prior to observation. Imagine a cat placed in a sealed box that also contains a vial of some poisonous gas and a mechanical hammer. The hammer is activated by a radioactive material with a Geiger counter and once activated it can break the vial releasing the gas. The radioactive atoms will disintegrate and the probability of their disintegration can be calculated precisely according to quantum mechanics rules. Suppose that the probability of the hammer being activated after thirty minutes is fifty percent. Then after thirty minutes the probability of the cat being dead is fifty percent but the probability of its being alive is also fifty percent.

When the box is opened after an hour the observer will find the cat either dead or alive. But prior to the observation, according to quantum mechanics the cat is fifty percent alive and fifty percent dead, which is physically absurd. In quantum mechanics, though, a system can be in several states each with a certain probability. This is called superposition of states. It is only through observation that the state vector reduction (wave function collapse) occurs. In quantum mechanical measurements it is the human consciousness, which causes the wave function collapse. Thus in Copenhagen interpretation the mathematical formulation had to be supplemented with philosophy in order to make any physical sense.

The question as to what is real and what is unreal belongs to the realm of philosophy. Our perception of the external world is what the mind projects after processing the information presented by the sensory organs. This is the perceived reality while the world outside is the objective reality. But this objective reality is constantly changing and depends on something else that may be called the ultimate reality. The perceived and objective realities represent what is observed and the ultimate reality represents what is.

Platos words are simply an alternate expression of the assertion of quantum physics that if there is no observer, there is no observation and no system. What is there is a set of possibilities or potentialities and the set is real in a different sense.

Quantum physics deals with the subatomic world, which is inaccessible to sensory perception. In the macroscopic physical world the role of the observer has to be viewed from a different perspective. When the observer stops looking at an object it does not cease to exist. The star, you were looking at, continues to be in the sky even if you stop looking. But it is not the same star that you looked at before; it, like everything else, is changing constantly. The point here is that in space-time continuum there are no objects but simply events. If an event is not observed, there is no way of ascertaining whether it actually occurred or not. This uncertainty puts the reality of the event in question.