...century of agnosticism about the true nature of matter hasn’t
found its way deeply enough into other fields, where materialism still
appears to be the most sensible way of dealing with the world and, most
of all, with the mind. Some neuroscientists
think that they’re being precise and grounded by holding tightly to
materialist credentials. Molecular biologists, geneticists, and many
other types of researchers – as well as the nonscientist public – have
been similarly drawn to materialism’s seeming finality.
But this conviction is out of step with what we physicists know about
the material world – or rather, what we don’t know.

The equation *F = ma* gave you two things that matter most to the
Newtonian picture of the world: a particle’s location and its velocity.
This is what physicists call a particle’s state. Newton’s laws gave you
the particle’s state for any time and to
any precision you need. If the state of every particle is described by
such a simple equation, and if large systems are just big combinations
of particles, then the whole world should behave in a fully predictable
way. Many materialists still carry the baggage
of that old classical picture.

But to account for all the new phenomena physicists were finding (ones
Newton knew nothing about), the Austrian physicist Erwin Schrödinger had
to formulate a very different kind of equation.
When calculations are done with the Schrödinger equation, what’s left
is not the Newtonian state of exact position and velocity. Instead, you
get what is called the wave function (physicists refer to it as psi
after the Greek symbol Ψ used to denote it).
Unlike the Newtonian state, which can be clearly imagined in a
commonsense way, the wave function is an epistemological and ontological
mess. The wave function does not give you a specific measurement of
location and velocity for a particle; it gives you only
probabilities at the root level of reality. Psi appears to tell you
that, at any moment, the particle has many positions and many
velocities. In effect, the bits of matter from Newtonian physics are
smeared out into sets of potentials or possibilities.

The wave function treats all properties of the particle
(electric charge, energy, spin, etc) the same way. They all become
probabilities holding many possible values at the same time. Taken at
face value, it’s as if the particle doesn’t have definite
properties at all.

According to the standard way of treating the quantum calculus, the act
of making a measurement on the particle kills off all pieces of the wave
function, except the one your instruments register. The wave function
is said to
*collapse* as all the smeared-out, potential positions or velocities vanish in the act of measurement.

...there are multiple interpretations of quantum theory, each of
which corresponds to a very different way of regarding matter and
everything made of it – which, of course, means
*everything*. The earliest interpretation to gain force, the
Copenhagen interpretation, is associated with Danish physicist Niels
Bohr and other founders of quantum theory. In their view, it was
meaningless to speak of the properties of atoms in-and-of-themselves.
Quantum mechanics was a theory that spoke only to our knowledge of the
world. The measurement problem associated with the Schrödinger equation
highlighted this barrier between epistemology and ontology by making
explicit the role of the observer (that is:
us) in gaining knowledge.

Some pinned their hopes on the discovery of hidden variables – a
set of deterministic rules lurking beneath the probabilities of quantum
mechanics. Others took a more extreme view. In the many-worlds
interpretation espoused by the American physicist Hugh
Everett, the authority of the wave function and its governing
Schrödinger equation was taken as absolute. Measurements didn’t suspend
the equation or collapse the wave function, they merely made the
Universe split off into many (perhaps infinite) parallel
versions of itself. Thus, for every experimentalist who measures an
electron *
over here,* a parallel universe is created in which her parallel copy finds the electron
*over there.*

Here is an even more important point: as yet there is no way to
experimentally distinguish between these widely varying interpretations.
Which one you choose is mainly a matter of philosophical temperament.
As the American theorist Christopher Fuchs puts
it, on one side there are the *psi-ontologists* who want the wave function to describe the objective world ‘out there’. On the other side, there are the
*psi-epistemologists* who see the wave function as a description of our knowledge and its limits.....The
real problem is that, in each case, proponents are free to single out
one interpretation over others because … well … they like it. Everyone,
on all sides, is in the same boat. There can be no appeal to the
authority of ‘what quantum mechanics says’, because quantum mechanics
doesn’t say much of anything with regard to its own interpretation.

First, the differences between the psi-ontological and
psi-epistemological positions are so fundamental that, without knowing
which one is correct, it’s impossible to know what quantum mechanics is
intrinsically referring to.
A second and related point is that, in the absence of experimental
evidence, we are left with an irreducible democracy of possibilities.

The high ground of materialism deflates when followed
to its quantum mechanical roots, because it then demands the acceptance
of metaphysical possibilities that seem no more ‘reasonable’ than other
alternatives.

[...Then this:...]

Some consciousness researchers see the hard problem as
real but inherently unsolvable; others posit a range of options for its
account. Those solutions include possibilities that overly project mind
into matter. Consciousness might, for example,
be an example of the emergence of a new entity in the Universe not
contained in the laws of particles. There is also the more radical
possibility that some rudimentary form of consciousness must be added to
the list of things, such as mass or electric charge,
that the world is built of.