**QUANTUM MECHANICAL THEORIES OF CONSCIOUSNESS**

**Abstract**

*Quantum mechanical theories of consciousness are contrasted to
classical ones. A key difference is that the quantum laws are
fundamentally psychophysical and provide an explanation of the causal
effect of conscious effort on neural processes, while the laws of
classical physics, being purely physical, cannot. The quantum approach
provides causal explanations, deduced from the laws of physics, of
correlations found in psychology and in neuropsychology..*

**Introduction**

Isaac Newton initiated in the seventeenth century an approach to
understanding nature that, with important contributions from Clerk
Maxwell and Albert Einstein, developed into what is called classical
mechanics. That theory is now known to be fundamentally incorrect. It
was replaced around 1926 by a profoundly different theory called quantum
mechanics. A principal conceptual difference between classical mechanics
and its quantum successor is that the former is exclusively physical
whereas the latter is essentially psychophysical. In particular,
classical mechanics is theory of a material physical world conceived to
be completely specified by numbers assigned to points in space and time,
and to be, moreover, dynamically complete, in the sense that the
behavior of these numbers for all times is completely specified by laws
and initial conditions that involve only these numbers themselves.
Contrastingly, orthodox quantum mechanics brings into the dynamics
certain conscious choices that are not determined by the currently known
laws of physics but have important causal effects in the physical world.

The entry of these causally efficacious conscious choices into
contemporary physics has led some quantum physicists to believe that an
adequate scientific theory of the conscious brain must be quantum
mechanical. This view is challenged by some non-physicists, who argue
that quantum theory deals with microscopic atomic-level processes
whereas consciousness is associated with macroscopic neuronal processes,
and that the concepts of classical physics provide an adequate
understanding of such macroscopic systems.

That argument is not valid. Quantum mechanics deals with the observed
behaviors of macroscopic systems whenever those behaviors depend
sensitively upon the activities of atomic-level entities. Brains are
such systems Their behaviors depend strongly upon the effects of, for
example, the ions that flow into nerve terminals. Computations show that
the quantum uncertainties in the ion-induced release of neurotransmitter
molecules at the nerve terminals are large (Stapp, 1993, p.133, 152).
These uncertainties propagate in principle up to the macroscopic level.
Thus quantum theory must be used in principle in the treatment of the
physical behavior of the brain, in spite of its size.

The entry into quantum dynamics of experiential elements, and in
particular of our conscious choices, is rendered possible by the
effective elimination from quantum mechanics of the classical concept of
material substance. Quantum theory retains the core feature of classical
physics, namely a structure of mathematical quantities assigned to
points in space and time. But both the behavior and the significance of
this structure is greatly altered. The mathematical structure represents
no longer a classically conceived material universe but rather an
*informational structure* that represents, in effect, the *knowledge*
associated with *psychophysical events* that have already occurred, and
also certain *objective tendencies* (propensities) for the occurrence of
future psychophysical events This conceptual revision is epitomized by
the famous pronouncement of Heisenberg (1958, p.100):

"The conception of objective reality of the elementary particles has
thus evaporated not into the cloud of some obscure new reality concept
but into the transparent clarity of a mathematics that represents no
longer the behavior of particles but rather our knowledge of this
behavior."

The aim of this chapter is to explain briefly, in plain words, how this
enormous change came about, how it works, and how this altered
conception of the role of consciousness in physics impacts on psychology
and neuroscience.

**Origin of quantum mechanics**

Quantum mechanics was initiated by a discovery made by Max Planck in
1900. Planck was studying the distribution over frequencies of the
radiant energy emitted from a tiny hole in a hollow container. Classical
physics gave clear predictions about the dependence of this energy
distribution upon the temperature of the container, but those
predictions did not match the empirical facts.

Planck found that the empirical data could be accounted for if one
assumed that the radiant energy associated with each given frequency was
concentrated in units, or quanta, with the amount of energy in a unit
being directly proportional to the frequency of the radiation that
carried it. The constant of proportionality was measured by Planck, and
is called Planck's constant.

This discovery was followed by a flood of empirical data that tested
various predictions of classical physics that depended sensitively on
the classical conceptions of such things as electrons and
electro-magnetic radiation. The data revealed fascinating mathematical
structures, which seemed to involve Planck's constant, but, like
Planck's data, was essentially incompatible with the classical
materialist conception of the world.

Many of the best mathematicians of the generation, men such as Hilbert,
Jordan, Weyl, von Neumann, Born, Einstein, Sommerfeld, and Pauli,
struggled to unravel this mystery, but it was not until 1925 that the
key step was made. Heisenberg found that correct predictions could be
obtained if one transformed classical mechanics into a new theory by a
certain "quantization" procedure. This procedure replaced the *numbers*
that specified the structure of the classically conceived material
universe by *actions*. Actions differ from numbers in that the ordering
of numerical factors does not matter\-\--2 times 3 is the same as 3
times 2\-\--whereas the order in which two actions are applied can
matter.

**Problems of interpretation**

This replacement of numbers by actions is the mathematical foundation of
quantum mechanics. But an adequate physical theory requires more than
just mathematical rules. It requires also a conceptual framework that
allows certain mathematical statements to be tied to human experiences.
In classical mechanics the interpretive framework that ties the
mathematics to experience does not disturb the mathematics. It
*envelops* the mathematical structure *but does not affect it*. The
basic idea of the classically conceived connection between the
physically and psychologically described aspects of nature is a
carry-over from the planetary dynamics that was the origin of classical
mechanics: the locations of objects are regarded as being directly
knowable, without producing any effects on those objects. But in quantum
mechanics the numbers that in classical mechanics represent, for
example, the locations of various material objects are replaced by
actions. These actions are associated with *the process of acquiring
information* or knowledge pertaining to the location of that object, and
this action normally affects the state that is being probed: the act of
acquiring knowledge about a system becomes entangled in a non-classical
way with the information-bearing quantum mechanical state of the system
that is being probed.

This elimination of the numbers that were imagined to specify the
physical state of the material world, and their replacement by actions
associated with the acquisition of knowledge, raises huge technical
difficulties. The needed conceptual adjustments were worked out
principally by Bohr, Heisenberg, Pauli, and Born. The center of this
activity was Bohr's institute in Copenhagen, and the conceptual
framework created by these physicists is called The Copenhagen
Interpretation.

**The Copenhagen interpretation**

A key feature of the new philosophy is described by Bohr:

> In our description of nature the purpose is not to disclose the real
> essence of phenomena but only to track down as far as possible
> relations between the multifold aspects of our experience. (Bohr,
> 1934, p.18)
>
> \...the appropriate physical interpretation of the symbolic quantum
> mechanical formalism amounts only to prediction of determinate or
> statistical character, pertaining to individual phenomena appearing
> under conditions defined by classical physics concepts. (Bohr, 1958,
> p.64).

The references to \`\"classical physics concepts\'\' are explained as
follows:

> \...it is imperative to realize that in every account of physical
> experience one must describe both experimental conditions and
> observations by the same means of communication as the one used in
> classical physics. (Bohr, 1958, p.88).
>
> The decisive point is to recognize that the description of the
> experimental arrangement and the recording of observations must be
> given in plain language suitably refined by the usual physical
> terminology. This is a simple logical demand since by the word
> "experiment" we can only mean a procedure regarding which we are able
> to communicate to others what we have done and what we have learnt
> (Bohr, 1958, p 3)

Bohr is saying that scientists do in fact use, and must use, the
concepts of classical physics in communicating to their colleagues the
specifications on how the experiment is to be set up, and what will
constitute a certain type of outcome. He in no way claims or admits that
there is an actual reality out there that conforms to the precepts of
classical physics.

But how can one use jointly and consistently these two mutually
inconsistent descriptions of nature? That is the problem that the
Copenhagen Interpretation solves, at least for all practical purposes.

**Quantum dualism**

The Copenhagen solution is to divide nature into two parts. One part is
the observing system, including the bodies, brains, and minds of the
human beings that are setting up the experimental situations and
acquiring, via experiential feedbacks, increments in knowledge. This
observing part includes also the measuring devices. This observing
system is described in ordinary language refined by the concepts of
classical physics. Thus the agent can say "I placed the measuring device
in the center of the room, and one minute later I saw the pointer swing
to the right." The agent's description is a description of what he
does\-\--of what probing actions he takes\-\--and of the *experienced*
consequences of his actions. The descriptions in terms of the language
and concepts of classical physics are regarded as part of this first
kind of description.

The other part of nature is the system being probed by the classically
conceived and described observing system. This probed system is
described in the symbolic language of quantum mathematics.

In classical physics the classical concepts are asserted to be
applicable in principle right down to the atomic level. But according to
the quantum precepts the quantum mathematical description must be used
for any properties of the atomic entities upon which observable features
of nature sensitively depend.

This separation between the two parts of nature is called the Heisenberg
cut. Above the cut one uses experience-based classical descriptions,
while below the cut one uses the quantum mathematical description.

The cut can be moved from below a measuring device to above it. This
generates two *parallel descriptions* of this device, one classical and
the other quantum mechanical. The quantum description is roughly a
continuous smear of classical-type states. The postulated theoretical
correspondence, roughly, is that the smeared out mathematical quantum
state specifies the *statistical weights* of the various alternative
possible classically described experienceable states. The predictions of
the theory thereby become, in general, statistical predictions about
possible experiences described in the conceptual framework of classical
physics.

There is, however, a fly in the ointment: In order to extract
statistical predictions about possible experiences, some specific
probing question must be physically posed. This probing question must
have a *countable* set of experientially distinct alternative possible
responses. "Countable" means that the possible responses can be placed
in one-to-one correspondence with the whole numbers 1, 2, 3, ..., or
with some finite subset of these numbers. But the number of possible
classically describable possibilities is not countable: there is a
continuous infinity of such possibilities. So some decision must be made
as to which of the possible probing questions will be physically posed.

**Conscious choices**

The mathematical structure of the theory does not specify what this
question is, or even put statistical conditions on the possibilities.
Thus the mathematical theory is dynamically incomplete on three counts:
it fails to specify *which* probing question will be posed, *when* it
will be posed, and *what* response will then appear. The theory does,
however, assign a statistical weight (probability) to each of the
alternative possible responses to any question that could be posed.

Von Neumann gave the name *Process 1* to the physical posing of a
probing question. He specified its general mathematical form, and
sharply distinguished it from the very different Process 2, which is the
mathematically specified *evolution* of the quantum state in accordance
with the rules specified by the quantization procedure. Process 1 events
*intervene* abruptly, from time to time, in the orderly evolution
specified by Process 2.

How does orthodox Copenhagen quantum theory resolve this critical
problem of the mathematical indeterminateness of the choices of the
needed Process 1 probing actions?

**Quantum Agents**

This problem of the indeterminateness of the conscious choices is
resolved in orthodox Copenhagen quantum mechanics by adopting a
pragmatic stance. The theory is considered to be a set of rules useful
to a community of communicating, conscious, observing agents imbedded in
a physical universe. These agents make conscious decisions about how to
probe that universe, in order to observe responses that will augment
their knowledge. The difficulty mentioned above, which is that the known
laws do not determine which of the possible probing questions will be
physically posed, is neatly resolved by saying that this very openness
*allows the conscious agents to freely choose* which probing questions
they will physically pose. Thus the causal gap in the mathematically
described structure is filled by the free choices made by conscious
agents.

Bohr often emphasized the freedom of these agents to make these choices:

> The freedom of experimentation, presupposed in classical physics, is
> of course retained and corresponds to the free choice of experimental
> arrangement for which the mathematical structure of the quantum
> mechanical formalism offers the appropriate latitude. (Bohr, 1958,
> p.73).
>
> To my mind there is no other alternative than to admit in this field
> of experience, we are dealing with individual phenomena and that our
> possibilities of handling the measuring instruments allow us to make a
> choice between the different complementary types of phenomena that we
> want to study. (Bohr, 1958, p. 51).

These quotes highlight the key fact that selection of the Process 1
probing events is determined, within the framework of contemporary
physics, not by known mathematical or physical laws but rather by free
choices made by conscious agents.

**Von Neumann's Move**

John von Neumann formulated Copenhagen quantum mechanics in a
mathematically rigorous form, and then, in order to remove ambiguities
associated with the placement of the Heisenberg cut, showed that this
cut could be pushed all the way up, so that the entire physically
describable universe, including the bodies and brains of the agents, are
described quantum mechanically. This placement of the cut does not
eliminate the need for Process 1. It merely places the physical aspect
of the Process 1 psychophysical event in the brain of the conscious
agent, while placing the conscious choice of which probing question to
pose in his stream of consciousness. That is, the conscious act of
choosing the probing question is represented as a psychologically
described event in the agent's mind, which is called by von Neumann
(1955, p. 421) the "abstract ego". This choice is physically and
functionally implemented by a Process 1 action in his brain. The
psychologically described and physically described actions are the two
aspects of a single psychophysical event, whose physically described
aspect intervenes in the orderly Process 2 evolution in a mathematically
well defined way.

Bohr emphasized that the laws of quantum theory should continue to be
valid in biological systems, but that the latitude introduced by the
severe constraints upon observation imposed by the demands of sustaining
life could permit such concepts such as "teleology" and "volition" to
come *consistently* into play. (Bohr, 1958, p.10, p.22)

**Interactive dualism**

Orthodox quantum theory is a theory of a type called interactive
dualism, which goes back in modern philosophy to Descartes, and before
that to the ancient Greeks. An interactive dualism postulates the
existence of two entirely different kinds of realities, mental and
physical, that interact. Mental realities have the character of
*feelings*, broadly construed to include thoughts, ideas, perceptions,
pains, joys, sorrows and all things that enter directly into our streams
of conscious experiences, and are described basically in psychological
language. Physical realities are elements that are described in our
theories of nature in terms of mathematical qualities assigned to
space-time points.

Interactive dualism combined with the precepts of classical physics
gives *classical* interactive dualism. This has been attacked
ferociously by philosophers for over three hundred years, with an
intensity that has been increasing over the past half century. *Quantum*
interactive dualism is based, instead, on orthodox (von Neumann) quantum
theory.

The first main objection to classical interactive dualism is that it
postulates the existence of two entirely different kinds of things, but
provides no understanding of how they interact, or even can interact.
The second main objection is that the physical description is, by
itself, already causally complete, giving a completely deterministic
account of the evolution in time of every physically described entity,
which means that the mental realities have nothing to do, and no
possibility of influencing anything physical. The mental side is a
"ghost in the machine" that is imagined to be pulling the levers in
order to 'work its will' in the physical world, but cannot really be
doing so because the behavior of the physically described universe is
completely determined independently of the ghostly machinations.

Quantum interactive dualism neatly evades both objections. The answer to
the first is that the form of the interaction between the mentally and
physically described aspects of nature *is specified* in von Neumann's
account of the measurement process. This account is part of a careful
mathematical description of the fundamental principles of quantum
theory, and of how they are to be employed in practice. The
specification of the form of the interaction between the two differently
described aspects is an essential part of von Neumann's formulation of
quantum theory. It is essential because quantum theory is specifically
designed to be a tool that allows physicists to make computations that
connect their experiences about setting up probing experiments to their
expectations about the observable responses to these probing actions.
Such a theory requires an adequate theory of measurement and
observation, which von Neumann provides.

As regards the second objection, a huge essential difference between the
classical and quantum dualities is that in the quantum case the
physically described part is not causally complete. Something else is
needed to complete the dynamics. Mental realities function both to
complete the causal structure and also to undergird what the theory is
basically about, namely the structural relationships between the
elements in our streams of conscious experiences.

In my characterization of interactive dualism I spoke of two kinds of
*realities*, physical and mental. Mental realities are certainly real: a
presently felt pain really does exist. The experiencings of theoretical
ideas in the streams of consciousness of physicists are also real
happenings. But the existence in nature of real entities that have all
the properties ascribed by the precepts of classical physics to, say,
"electrons" would be surely denied by most quantum physicists. Quantum
philosophy recommends avoiding commitment to the idea that there are
realities in nature that accurately conform to our theoretical ideas
about the physical universe. In regard to the physical it is only the
*descriptions* themselves, and the way that they are used, that are
ascribed significance in orthodox quantum philosophy. Ontological
commitments pertaining to the physical are not part of science. In
general, the practical meanings of descriptions are defined in the end
by how the descriptions are used in practice.

The fact that the form of the interaction between the psychologically
and physically described aspects of quantum theory is specified is
important: it severely constrains the theory. Arbitrary ad hoc proposals
cannot be postulated willy nilly. For example, many proposals are ruled
out by the fact the living brain is large, warm, and wet, and interacts
strongly with its environment. The first, and very stringent, demand on
any serious proposal is that it work in this hostile-to-quantum-effects
setting.

The *only* pertinent quantum effect known to me that survives robustly
under these hostile settings is the quantum Zeno effect, so-named
because of its rough similarity to the paradox that claims that the hare
can never catch the turtle because, by the time the hare reaches where
the turtle was, the turtle will have moved on. That claim is obviously
false. But there is a vaguely similar claim about quantum mechanics that
is unquestionably true (Misra, 1977). If, under appropriate conditions,
one repeatedly poses the same probing question at a sufficiently rapid
rate, then the sequence of responses will tend to get stuck in place. In
the limit of arbitrarily rapid re-posings, the response will become
frozen: all the responses will come out to be the same, even though very
strong physical forces may be working to make them change. Thus a
manipulation of the *timings* of the probing actions, which are under
the control of the consciousness of agent, can have, *even in a warm,
wet brain*, a very special kind of physical effect. If, by mental
effort, an agent can cause a sufficient increase in *probing rate,* then
that agent can cause a state of intention and attention to be held in
place much longer than would be the case if no such effort were being
made.

The crucial point, here, is that the physically-described laws of
quantum mechanics do not fix the *times* at which the physical Process 1
probing actions occur, or *what* these physical probing actions will be.
This lacuna is the essential reason why the conscious "free choices" on
the part of human agents were brought into quantum mechanics by its
founders, and were retained by John von Neumann! These *conscious
choices* control the timings of the physical Process 1 events studied by
Misra and Sudarshan, and this connection entails, in principle, the
capacity of these psychologically described aspects of the streams of
consciousness of agents to control, via quantum Zeno holding actions,
certain physically described features of the world.

Huge survival benefits could accrue to agents that can exploit this
feature of the quantum mechanics, because this intentional stabilizing
of attention would hold in place also the corresponding pattern of
functional brain activity.

Such a holding effect could, of course, be *postulated,* ad hoc*,* to
occur in a classical-physics-based model. But in that case the holding
effect would not be a direct consequence of the same basic
psychophysical laws that are used by physicists to explain atomic
phenomena. In the quantum case the holding effect is probably the only
robust kind of effect of mind on brain that the theory predicts, whereas
any desired regularity could postulated in a theory that simply adds
mind ad hoc. As regards classical-physics-based theories, the view of
physicists is that classical physics is an *approximation* to quantum
physics. All effects of conscious thought upon brain activity that
*follow* from quantum theory, such as the quantum Zeno holding effect,
are eliminated in the classical physics approximation, because in that
approximation the uncertainty-principle-based latitude within which the
causal effects of mind upon the physically described aspects of nature
operate shrinks to zero.

**Comparison to psychological findings**

The dynamical effect described above of a volition-induced high rapidity
of the Process 1 probing actions is exactly in line with the description
of the effects of volition described by William James (1892). In the
section entitled *Volitional effort is effort of attention* he writes:

Thus we find that we reach the heart of our inquiry into volition

when we ask by what process is it that the thought of any

given action comes to prevail stably in the mind. (p. 417)

The essential achievement of will, in short, when it is most

'voluntary,' is to attend to a difficult object and hold it fast

before the mind. (p.417).

Everywhere, then, the function of effort is the same: to keep

affirming and adopting the thought which, if left to itself, would slip
away.

(p.421)

James may have foreseen, on the basis of his efforts to understand the
mind-brain connection, the eventual downfall of classical mechanics. He
closed his book with the prophetic words

> ...and never forget that the natural-science assumptions with which we
> started are provisional and revisable things. (p.433)

A lot has happened in psychology since the time of William James, but
these newer developments support James's idea of the
holding-attention-in-place action of volition. Much of the recent
empirical and theoretical work pertaining to attention is summarized in
Harold Pashler's book *The Psychology of Attention* (Pashler, 1998).
Pashler concluded that the evidence indicates the existence of two
distinct kinds of mental processes, one that appears not to involve
volition, and that allows several perceptual processes to proceed in
parallel without significant interference, and one that does involve
volition and that includes planning and memory storage. This latter
process seems to involve a linear queuing effect with limited total
capacity.

These properties of volition-driven processes appear to be *explainable*
in terms of the basic laws of orthodox quantum physics, which entail the
existence of Process 1 physical events whose timings are controlled by
conscious choices, and which can, in principle, by means of the quantum
Zeno effect, tend to hold in place a pattern of neural activity that
will tend to bring into being an intended effect. But this holding
effect drops out in the classical-physics approximation, in which all
physically described properties become completely determined by
physically described properties alone, with consciousness a causally
inert, or causally superfluous, bystander. *Correlations* between
physically and psychologically described properties can be described
within a classical physics based framework, but the psychologically
described aspects will remain essentially epiphenomenal by-products of
brain activity.

This evidence from psychology is discussed in detail in Stapp (1999,
2001) and in Schwartz, Stapp, and Beauregard (2003, 2005)

**Application in Neuroscience**

The most direct evidence pertaining to the effects of conscious choices
upon brain processes comes from experiments in which identifiable
consciously controllable cognitive processes *seem to be* controlling
directly measured physical processes in the brain. An example is the
experiment of Ochsner et.al. (2001). The subjects are trained how to
cognitively re-evaluate emotional scenes by consciously creating and
holding in place an alternative fictional story of what is really
happening in connection with a scene they are viewing.

> The trial began with a 4 sec presentation of a negative or neutral
> photo, during which participants were instructed simply to view the
> stimulus on the screen. This interval was intended to provide time for
> participants to apprehend complex scenes and allow an emotional
> response to be generated that participants would then be asked to
> regulate. The word Attend (for negative or neutral photos) or
> Reappraise (negative photos only) then appeared beneath the photo and
> the participants followed this instruction for 4 sec ...
>
> To verify whether the participants had, in fact, reappraised in this
> manner, during the post-scan rating session participants were asked to
> indicate for each photo whether they had reinterpreted the photo (as
> instructed) or had used some other type of reappraisal strategy.
> Compliance was high: On less than 4% of trials with highly negative
> photos did participants report using another type of strategy.

Reports such as these can be taken as evidence that the streams of
conscious of the participants do exist and contain elements identifiable
as efforts to reappraise.

Patterns of brain activity accompanying reappraisal were assessed by
using functional magnetic imaging resonance (fMRI). The fMRI results
were that reappraisal was positively correlated with increased activity
in the left lateral prefrontal cortex and the dorsal medial prefrontal
cortex (regions thought to be connected to cognitive control) and
decreased activity in the (emotion-related) amygdala and medial
orbito-frontal cortex.

How can we understand and explain the psychophysical correlations
exhibited in this experiment?

According to the quantum model, the conscious feelings *cause* the
changes in brain activity to occur. This causation is in strict
conformity to the known laws of physics, as spelled out in von Neumann's
book *Mathematical Foundations of Quantum Mechanics*.

This causal explanation, this whole causal story, falls apart if one
tries to explain this psychophysical correlation within the framework of
the classical approximation. That approximation entirely eliminates the
effects of our conscious choices and efforts upon the physical world,
including our brains. But what is the rational motivation for insisting
on using this approximation? The applicability of the classical
approximation to this phenomenon certainly does not follow from physics
considerations: calculations based on the known properties of nerve
terminals indicate that quantum theory must in principle be used. Nor
does it follow from the fact that classical physics works reasonable
well in neuroanatomy or neurophysiology: Quantum theory explains why the
classical approximation works well in those domains. Nor does it follow
rationally from the massive analyses and conflicting arguments put forth
by philosophers of mind. In view of the turmoil that has engulfed
philosophy during the three centuries since Newton cut the bond between
mind and matter, the re-bonding achieved by physicists during the first
half of the twentieth century must be seen as an enormous development: a
lifting of the veil. Ignoring this huge and enormously pertinent
development in basic science, and proclaiming the validity of
materialism on the basis of inapplicable-in-this-context nineteenth
century science is not a rational judgment.

Of course, one can simply abandon the idea that ideas can actually
*cause* anything physical, and view the feeling of effort as not a
*cause,* but rather an *effect,* of a prefrontal excitation that causes
the suppression of the limbic response, and that is caused entirely by
other purely physical activities.

Viewed from a sufficiently narrow perspective that might seem to be a
satisfactory conclusion, but it leads to the old problem: why is
consciousness present at all, and why does it feel so causally
efficacious, if it has no causal efficacy at all? Why this big hoax?
Quantum theory answers: There is no a hoax! It was only the premature
acceptance a basically false physical theory, fundamentally inapplicable
to the brain, that ever made it seem so!

The only objections I know to applying the basic principles of physics
to brain dynamics are, first, the forcefully expressed opinions of some
non-physicists that the classical approximation provides an entirely
adequate foundation for understanding brain dynamics, in spite of the
quantum calculations that indicate the opposite; and, second, the
opinions of some physicists that the hugely successful orthodox quantum
theory, which is intrinsically dualistic, should, for philosophical
reasons, be replaced by some theory that re-converts human consciousness
into a causally inert witness to the mindless dance of atoms. Neither of
these opinions has any secure scientific basis.

There are several other quantum theories of consciousness, but all of
them are based on von Neumann's work. The physics considerations
described above rest completely on that work. I shall describe next some
proposals that go far beyond von Neumann's secure base, and introduce
some very controversial ideas.

**The Penrose-Hameroff Theory**

Roger Penrose and Stuart Hameroff (Hameroff & Penrose, 1996) have
proposed a quantum theory of consciousness that brings together three
exciting but controversial ideas. The first pertains to the
still-to-be-worked-out quantum theory of gravity. The second involves
the famous incompleteness theorem of Gödel. The third rests upon the
fairly recently discovered microtubular structure of neurons.

Penrose proposes that the abrupt changes of the quantum state that are
associated with conscious experiences are generated by the gravitational
effects of particles of the brain upon the structure of space-time in
the vicinity of the brain. Ordinarily one would think that the effects
of gravity *within the brain* would be too minuscule to have any
significant effect on the functioning of the brain. But Penrose and
Hameroff come up with an estimate of typical times associated with the
gravitational effects that are in the tenth of a second range associated
with conscious experiences. This fuels the speculation that the abrupt
changes in the quantum state that occur in quantum theory are caused not
by the entry of thoughts into brain dynamics, but by quantum effects of
gravity.

But then why should thoughts or consciousness be involved at all?

Two reasons are given. Penrose uses Gödel's incompleteness theorem to
argue that mental processing cannot be wholly mechanical or algorithmic.
The argument takes hundreds of pages (Penrose, 1986, 1994) and has been
attacked by many seemingly qualified critics. (e.g., Putnam, 1994). It
is fair to say that it has not passed the usual demands made upon
mathematical and logical arguments. But the argument claims that both
mental processing and the gravitational effects are non-algorithmic, and
that the latter could therefore provide in a natural way the
non-algorithmic element needed for the former

The second connection of the proposed gravitational effect with
consciousness is that the estimated time associated with the
gravitational effect was based on the presumption that the components of
the brain critical to consciousness were functioning microtubules. Data
pertaining to loss of consciousness under the influence of various
anesthetic agents indicate that the proper functioning of microtubules
is necessary for consciousness. But many things are *necessary* for
consciousness, so this argument that the gravitational effect is
connected consciousness via microtubules is not compelling. *.*

A serious objection to the Penrose-Hameroff theory has been raised by
Max Tegmark (2000). The Penrose-Hameroff theory requires that the
critical microtubular state be a *coherent* quantum state that extends
over a macroscopic region in the brain. Normally one expects any
macroscopic coherence of a quantum state in a warm wet brain to be
destroyed almost immediately. Tegmark estimates the duration of
coherence to be on the order of 10^-13^ seconds, which is far smaller
than the one tenth of a second associated with conscious events. Hagen,
Hameroff, and Tuszynski (2002) have claimed that Tegmark's assumptions
should be amended, so that the decohence time increases to 10^-4^
seconds, and they suggest that the remaining factors can perhaps be made
up by biological factors. In any case, the need to maintain macroscopic
quantum cohererence in a warm wet brain is certainly a serious problem
for the Penrose-Hameroff model.

It might be mentioned here that in the von Neumann model described in
the preceding sections quantum decoherence is an important *asset,*
because it allows the quantum state of the brain to be understood as
essentially a smeared out statistical ensemble (i.e., collection) of
essentially classically conceived states, which, however, can interact
with neighboring members of the ensemble in a way that preserves the
quantum Zeno effect. This quasi-classical conceptualization of the
quantum state of the brain allows non-physicists to have a relatively
simple understanding of the mind-brain system.

**The Eccles-Beck approach**

An early quantum approach to the mind-brain problem was made by John
Eccles (1990) who emphasized the entry of quantum effects into brain
dynamics in connection with effects at nerve terminals. However, instead
of building directly on the quantum rules and the profound conceptual
relationships between quantum and classical mechanics he introduced a
conscious biasing of the quantum statistical rules. This actually
contradicts the quantum rules, thereby upsetting the logical coherency
of the whole scheme. In a later work with Beck (2003) he retained the
quantum rules, while introducing quantum uncertainties at the nerve
terminals that can play the same role that they do in the standard
approach described earlier. This brings the model into accord with the
standard model described above, in regard to this technical point.
However, Eccles added a superstructure involving conscious "souls" that
can exist apart from physical brains. That suggestion goes beyond the
ideas described here.

**Other Theories**

Several other quantum theories of consciousness have been proposed.
\[Bohm, 1990; Jibu, 1995\]. All are outgrowths of von Neumann's
formulation. The differences in these proposals are mainly at the level
of technical physics. I have focused here on the over-riding general
issues of why quantum theory should be relevant to consciousness in the
first place, and how the switch to quantum physics impacts upon the
question\-\--vital to neuroscience, psychology, and philosophy\-\--of
the neural effects of volitional effort.

HENRY P. STAPP

Henry Stapp is a theoretical physicist with a long-time special interest
in mathematical and conceptual problems in the foundations of quantum
theory. He worked with Wolfgang Pauli and with Werner Heisenberg and has
published extensively on the subjects of axiomatic S-matrix theory,
quantum non-locality, philosophy of quantum theory, and the mind-brain
interaction.

**Further Reading**

The Emperor's New Mind, Roger Penrose

Mind, Matter, and Quantum Mechanics, Henry Stapp

The Large, the Small, and the human Mind, Roger Penrose (with

Abner Shimony, Nancy Cartwright, and Stephen Hawking)

The Mind and the Brain: Neuroplasticity and the power of mental force,
Jeffrey Schwartz and Sharon Begley

The Mindful Universe, Henry P. Stapp

**Acknowledgements**

I thank Max Velmans and Ed Kelly for influential comments on earlier
drafts.

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