[Marxism] The Notion of Absolute Truth

[Rakesh Bhandari <bhandari@xxxxxxxxxxxx>]

re: quantum mechanics. I can't wrap my head 
around the philosophical argument about Everett's 
interpretation, as provocative as it is.
rb

 The Tyranny of Common Sense
David Papineau
Sometimes I despair of my philosophical 
colleagues. They are so conservative. I don't 
mean this in a political sense. In conventional 
party-political terms, most professional 
philosophers are probably well to the left of 
centre. As a group, they have a strong sense of 
fairness and little commitment to the social 
status quo. But this political open-mindedness 
doesn't normally carry over to their day jobs. 
When it comes to philosophical ideas, they are 
inveterately suspicious of intellectual 
innovation. In their eyes, a good philosophical 
theory is one that agrees with the views found on 
the Clapham omnibus. Few philosophers, in the 
English-speaking world at least, think of 
philosophy as a source of radical new ideas. 
Rather they view it as way of systematising the 
everyday reactions of ordinary people.
What a dispiriting ambition. If I thought that 
this was all philosophy could do, I would quit 
straightaway. Common sense is boring enough to 
start with, even before it is dissected by 
analytic philosophers....

I myself have recently become interested in a 
rather different way in which recent scientific 
findings threaten to overturn our everyday view 
of the world. Here the evidence comes from 
quantum mechanics rather than psychological 
research. It will be worth spending the last part 
of this article explaining this issue in some 
detail. For it is possible that quantum theory 
will make us rethink nearly everything that we 
currently take for granted. This is because 
quantum theory suggests that our history is not 
the only history, but just one of many real 
histories, in fact one of all the physically 
possible histories, including histories in which 
The Philosophers' Magazine does not contain this 
article, and histories in which you went for a 
walk five minutes ago, not to mention histories 
in which you married a different spouse, and 
histories in which you do not exist at all.
Of course, this is a very strange view, and it 
should be said that it isn't endorsed by most 
practising physicists. But it may well be the 
only good way of understanding quantum mechanics. 
Quantum mechanics as understood by practising 
physicists is effectively incoherent, and the 
only way that physics students can be made to 
accept it is by being repeatedly told that it is 
unscientific to ask awkward questions. But among 
those who are ready to ask questions, the view 
that there must be multiple realities is fast 
gaining adherents.
The reasons are not too hard to understand. Let 
us start with the fact that quantum mechanics 
characterises microscopic systems, like a moving 
electron, say, by a mathematical device called a 
wave function. This function does not specify 
exact values for the position or velocity of the 
electron. Instead it specifies the probabilities 
that the electron will turn up with any of a 
number of different positions or velocities when 
it is measured. Because of this probabilistic 
element, a number of early interpreters of the 
theory, including Albert Einstein, concluded that 
quantum mechanics must be incomplete. Since 
electrons clearly do have exact positions and 
velocities, they reasoned, the wave function can 
only be a measure of our ignorance, a 
specification of the odds on the electron already 
being in some given place, even though we don't 
yet know which. This response has now been 
effectively discredited. For over fifty years 
ingenious physicists have been devising 
experiments to decide between Einstein and the 
view that the wave function is physically real, 
and the results have decided against Einstein 
every time. Electrons don't always have definite 
positions. Sometimes they really are in a 
"superposition" of all the different places 
allowed by their wave functions.
Quantum mechanics also contains an equation, 
called Schrödinger's equation, which specifies 
how the wave functions of microscopic systems 
will evolve smoothly and deterministically over 
time. This is analogous to the way that Newton's 
laws of motion determine the evolution of a 
body's position and velocity over time. Except 
that, where Newton's laws deal with actual 
positions and velocities, the Schrödinger 
equation describes the evolution of 
probabilities. So quantum mechanics, as normally 
understood, needs to appeal to another kind of 
process, in order to turn probabilities into 
actualities. This second process is commonly 
known as the "collapse of the wave function", and 
is supposed to occur when a measurement is made. 
So, for example, if the electron collides with a 
sensitive plate, and registers in a particular 
position, the probability for that position 
instantaneously jumps to one, and for all other 
positions to zero.
However, if you stop to think about it, this is 
little short of inconsistent. What qualifies the 
collision with the plate as a "measurement"? 
After all, the joint system of plate plus 
electron can itself be viewed as a large 
collection of microscopic particles. And as such 
the joint system will be characterised by a 
probabilistic wave function, which will then 
evolve smoothly in accord with the Schrödinger 
equation. >From this perspective, there will then 
be no collapse into an actual position after all, 
but simply probabilities of the electron's being 
in different places on the plate once more.
In practice, most physicists avoid the 
inconsistency by assuming that a wave-collapsing 
measurement occurs whenever a big enough physical 
system is involved. But how big is big enough? It 
seems arbitrary to draw the line at any 
particular point. This is the moral of 
"Schrödinger's cat". Imagine that some 
unfortunate cat is put in a chamber which will 
fill with poison if the electron registers on the 
left half of the plate, but not if the electron 
registers on the right half. Until the wave 
function collapses, reality remains undecided 
between the two possibilities, alive or dead. So 
when does reality decide? When the electron hits 
the plate? When the poison kills the cat? Or only 
when a human enters the room and sees if the cat 
is alive or dead? Nothing in quantum mechanics 
seems to provide any good answer.
What if reality never decides? That is, what if 
the wave function never collapses, with the 
electron therefore keeping positive probabilities 
both of being on the left and of being on the 
right of the plate, and the cat therefore keeping 
positive probabilities both of being alive and of 
being dead, and your brain therefore keeping 
positive probabilities both of seeing the cat 
alive and seeing it dead? At first sight this 
might seem to contradict our experience. When we 
look, we see either a live cat or a dead cat, not 
some mixture of both. But we need to ask: what 
exactly would it be like to have a brain whose 
wave function contained positive probabilities 
both for seeing a live cat and for seeing a dead 
cat? There is no obvious reason to suppose that 
this would be some kind of fuzzy experience, like 
seeing a superimposed photo of a live and dead 
cat. Instead, perhaps it would be like being two 
people, one of whom sees a dead cat, and the 
other a live cat.
According to this view, when an intelligent being 
interacts with a complex quantum system, its 
brain acquires a corresponding complexity, each 
element of which then underpins a separate centre 
of consciousness. One version of your brain sees 
a live cat, another a dead cat. It is as if 
reality has an extra dimension, alongside the 
familiar dimensions of time and space, with your 
brain, along with the cat and the poison, having 
different properties at different positions in 
this dimension.
Of course, if your two consciousnesses are both 
present in reality, we need some account of why 
neither becomes aware of the other. But this too 
can be explained. There are possible experimental 
circumstances, akin to those which showed 
Einstein wrong, that would demonstrate that your 
brain contained both live cat and dead cat 
perceptions. But with a system as complex as a 
human brain, these experiments are far too 
difficult to carry out. And this is why the live 
cat element in your brain never finds out about 
the dead cat element: even though both elements 
are present in reality, the precise circumstances 
which would allow them to influence each other 
are too complicated ever to occur.
The mathematical underpinnings of this 
no-collapse view of quantum mechanics were first 
worked out by Hugh Everett over forty years ago. 
Since then it has received very little attention 
from philosophers. Perhaps, given the points I 
have made above, this is unsurprising. It is 
harder to imagine anything further from common 
sense than Everettian metaphysics. This strongly 
disinclines philosophers from taking it 
seriously. But they may be making a big mistake. 
Of course, future developments in fundamental 
physics could come up with some alternative way 
of fixing quantum mechanics. But I wouldn't bet 
on it. It is not as if crazy theories from 
science have never turned out to be correct. 
(Think of the theory that the earth moves, or 
that the sun is a star, or that all matter is 
made of atoms.)
If Everett is right, a lot of common sense 
thinking will be quite wrong. For instance, take 
our everyday ideas about personal identity. We 
normally think of ourselves as beings that 
persist over time, and indeed such thinking is 
central to all our plans, projects and ambitions. 
But if Everett is right, we don't persist in the 
normal way, but are constantly splitting into 
multiple descendants, like amoebae. How exactly 
should we then think about the future, if there 
is no single "me" who will exist tomorrow?
Derek Parfit, one of the few contemporary 
philosophers who isn't in thrall to common sense, 
has long argued on independent grounds that it is 
better not to think of the future in terms of the 
survival of a single "me". But most of his 
arguments have hinged on outlandish 
science-fiction thought experiments, and this has 
allowed the majority of philosophical 
commentators to maintain that the conventional 
thinking about persons is quite adequate to our 
everyday purposes. This response will no longer 
be available if Everett is right. If we really 
are splitting all the time, we will have no 
alternative but to find some new way of thinking 
about our relationship to our futures.
Or consider probability. As we normally think of 
it, this is a measure of the objective 
uncertainty of future events. Different possible 
futures compete to be real, and their 
probabilities measure their current standings in 
this competition. But not so given Everettian 
metaphysics. Here all futures with a positive 
quantum mechanical chance (the cat lives, the cat 
dies) are sure to occur. Probability must mean 
something different.
Even if it doesn't measure uncertainty, 
probability will still be a guide to action: the 
most rational choice will still be the one that 
brings good things in the most probable future. 
But, where on orthodox thinking this was a matter 
of acting in the interests of the future self 
which is doing best in the competition to become 
real, on the Everettian view all your possible 
future selves will become real, and rational 
choice is a matter of favouring your 
high-probability actual successors over the 
low-probability ones. This makes a kind of sense 
- perhaps more sense in the end than orthodox 
thinking - but it is certainly not the way we 
normally think.
These are strange waters in which nobody really 
knows how to navigate. Yet, given the chances of 
Everettianism turning out true, it is surely a 
matter of some importance to know what it implies 
for our place in the universe. Moreover, this is 
an essentially philosophical task, for it will 
require us to unearth some of our deepest 
implicit assumptions, and hold them up to 
critical examination. It will be a great pity if 
contemporary philosophers fail to take up this 
challenge, simply because of their unreasonable 
fondness for the familiarities of common sense.
David Papineau is Professor of Philosophy of 
Science at King's College, London and author of 
The Roots of Reason and Thinking about 
Consciousness (Oxford University Press).

http://www.philosophersnet.com/magazine/printer_friendly.php?id=1005
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