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Tim asked:

Is it possible for an event to be non-causal? If so, what are the implications of non-causal events?

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According to quantum mechanics, there are uncaused events (such as the radioactive decay of an
atom, for example, or the precise way in which the QM probability wave function collapses). But some
people didn't like this idea ("God doesn't play dice with the Universe" Albert Einstein said), so they
posited what were called 'hidden variables' which would be unable to be measured but which would
cause quantum events. However, John Bell thought up an experiment that would distinguish whether
an event depended on hidden variables or not, and Alain Aspect found a way to do it. The results
showed that (on the assumptions made), there are no hidden variables.

Since all experiments rest on assumptions, we can look at them to see if there is a way out of the
conclusion. One of the assumptions here is that causes precede effects. If that is false, then we can
have backwards causation in time and the Aspect experiment does not show that there are uncaused
events. Some people take this seriously, but others think backwards causation is logically suspect. In
a way, you have to choose which you think is more impossible: backwards causation or uncaused
events.

I would think that the scientific consensus at the moment is that some events are uncaused.

As to the implications, there are many. One I think is important is that it becomes not just practically
but also theoretically impossible to predict the future in the way that La Place's demon could. The
demon would know the exact state of the world at some instant, and then, using the strict causality of
physical laws, be able to calculate the state of the world at some future time. If some events are
uncaused, this is no longer possible.

Some people think that uncaused events can explain free will, because they allow us out of the sort of
lock-step determinism that La Place argued for. I disagree. I want free will to mean that I choose what
to do for my own reasons, not that science can't predict what I will choose because some uncaused
events take place in my brain. If these events are uncaused, then they are not caused by me, and it
isn't mydecision any more.

Tim Sprod

Do you mean by "non-causal", "uncaused" or do you mean "not causing anything"? The problem, as I
see it, is that no one really knows what to make of causation. Hume dealt with it in a very stunning
and frustrating way (take a look at his Treatiseif you haven't), and most philosophers, as far as I can
tell, spend a lot of time listing types of causes and effects and taking cause more or less on intuitive
grounds. I'll take your meaning to be "uncaused".

Here's an example: suppose that there were a machine that could "read" the positions of all the
atoms, say, in a piece of matter (which are moving around or vibrating or whatever), and project
holographs of them, magnified a few million times, into the room. So the hologram is caused by the
lasers, which is caused by the reading mechanism, etc. Now clearly we don't want to say that the
images of the atoms or quarks or whatever in that picture are causing each other's motion, right? Why
not? Because our physical theories say they aren't; those are our physical intuitions. Let's take it one
step further; suppose (and I'm extrapolating from an example of Tye's here) that this "piece of matter"
is someone's living brain. Is the hologram conscious? Why not? Because it's "just pictures"? But
they're interacting just like the elements in the brain are, so why can't they be conscious? Believe it or
not, I've asked manypeople this question, and no one can really answer it; we just have an intuition
that the hologram can't be conscious, because of "causality".

So to get back to your question, now that I've muddled the waters of causality somewhat (and I've
only talked about linearcausality here...). in quantum physics, the answer to your question is pretty
unequivocally "yes". "Vacuum fluctuations" and "virtual particles" are the results of the uncertainty
principle, roughly speaking. That is, given that there is a lowest level of energy below which nature
cannot go, one filled with a kind of undifferentiated wave-function (which is a real entity, by the way)
which is (effectively, but actually it's in many states simultaneously and changing the likelihood of sets
of these) fluctuating very rapidly, the spontaneous production of particles and energy takes place all
the time. The vacuum is not a vacuum, in other words, but there isn't anything quite there either,
except occasionally. Are these events "caused"? Well, there's no simple and direct cause we know of.
There's also a phenomenon known as "tunneling", where a particle is quite suddenly and
spontaneously somewhere where it basically can't be, because it has a very low probability of being
there. How does that happen? It just happens, with some finite probability. Is it caused? Well, it can
be pushed in that direction, but no one can say that it will happen with certainty.

So the implications of these events are quite profound, actually. Whole electronic industries are built
on the tunneling effect, and huge (and well-verified, for the most part) theories make use of virtual
particles and vacuum fluctuations to explain, for example, the interactions of the quarks comprising
other particles.

Steven Ravett Brown

If you mean by a "non-causal event" an event that has no effect then I don't see why it should not be
possible. I agree with David Hume when he says that it is possible for an event not to have a cause,
so why shouldn't it be possible for an event not to have any effect? Of course, whether it is true or
even probable is another matter. I suppose that an event which had no effects would simply be some
isolated happening; lonely as a cloud.

Kenneth Stern