Notes:
So let’s begin with some ad hoc arguments that have been used for a better fit of quantum phyiscs than of classical physics.
In the first place is there the experience of free will. This is a very strong experience. In a survey that I did among freshman psychology students only a few percent claimed to have no free will. A substantial percentage of those students studied Articifical Intelligence.
Willima James who seriously considered a model of epiphenomenal consciousness like the one proposed by Daniel Dennett rejected this on the basis of the experience of free will.
Of course several scientists nowadays argue that although the experience is strong, it is nonetheless an illusion.
Classical Newtonian physics describes the world as a immense clockwork . Given well defined initial conditions the mechanics determine with arbitrary precision what will happen.
Such is not the case in quantum physics. Quantum physics predicts probabilities and cannot say anything about singular events. For instance the mean of the distribution of radioactive decay times can be predicted but this is impossible for a single radioactive decay. Einstein was very sceptical of this aspect of quantum physics. He said: God doens’t play with dice. He wanted to be able to predictthe outcome singular events and therefore thought that quantum physics was not complete. That something was missing. That something was called ‘hidden variable’.
We will see later that he was wrong in this belief.
Now it escapes me, but I am not a philosopher, why if chance plays a fundamental role this would enable free will. I see that a deterministic world doesn’tr allow for it so it may be that the chance aspect is in some way used.
The second aspect that is often mentioned in respect to quantum physics is the unity of consciousness.
Our conscious experiences are not made of atomic entitites. As James wrote the experience of lemonade is not the experience of lemon plus the experience of sugar. We cannot break up the experience in parts. This has become a rather crucial argument because we now know much more about brainprocessing of for instance visual stimuli and know that in the brain the sensory input is broken up in parts. Velocity, colour, form etc. etc. are often processed in separate sometimes far-away brain regions. In some way the experience integrates these different brain activities. Quantum physics has a holistic character partly because corpuscules have also a wave aspect( the so called wave particle dualism) but also because under specific conditions particles can loose their identity and act as a whole. And the aspect of non local correlations can bind even two quantum systems over infinite distances.
Finally the computational requirements of the brain are enormous. In Penrose’s theory therefore it is proposed that non conscious processing is like quantum computing. Quantum computing is intrinsically parallel. With a quantum computer it is possible to explore parallel solutions to a system with much less extra hardware costs than with parallel traditional computers. For a quantum computer the encryption codes that are used nowaday to make our internet secure can be broken in seconds while basically that problem is unsolvable with tradtional machinery. The proof of principle has been passed, there are 4 bit quantum computers so if we can build them why would nature in the course of the evolution not have been able to develop them? The evolutionary advantages are obvious.
All the 3 arguments above are not to be seen as convincing. But they illustrate why some scientists started to consider the idea that quantum physics might have to do with consciousness.