Re: QM & Causality

From: Andrew J Bacon (andrew.bacon_at_lmh.ox.ac.uk)
Date: 08/30/04 

Date: Mon, 30 Aug 2004 12:23:32 GMT

"robert j. kolker" <nowhere@nowhere.net> wrote in message
news:2pgbrqFk15s5U1@uni-berlin.de...
>
>
> Mike wrote:
>
> > We understand nothing as far as causality is concerned. We do not know
> > what causality is terms of a mechanical process manifested in
> > phenomena. All we have done is epistemic analysis of causality so far,
> > i.e. metaphysics.
>
> See the philosophy of David Hume on this issue: - An Enquiry into Human
> Understanding -. Cause is established in our minds by concurrence of
> events (i.e. correlation). Hume denied that we could establish necessary
> connection, however strong the concurrence.

Hume gave two different definitions of cause (which he mistakenly identified
as the same in his exposition). First a temporal one, and then a
counterfactual one, but as he thought they where the same he ignored the
counterfactual and expanded on the temporal one instead. The problem with
this is that the direction of the causal relation and the direction of the
temporal relation are, it would seem, not the same by necessity (see
Dummett - Bringing About The Past).
Hume was right however, that we cannot establish a necessary connection
between cause and effect, we can only establish this by induction. There
are people who would think other wise (e.g. Mackie) who postulate 'inus
conditions' which give necessary and sufficient conditions for an effect to
occur, this supposedly accounts for empirical anomolies when a cause is not
succeeded by its effect or an effect is not preceded by its cause. Most of
us would, however, prefer to settle for an account which denies sufficiency
and neccessity of causes, in favour of a probabilistic account, i.e. that
causes raise the probabilities of their effects, and connections can thus
be established by means of empirical induction (these accounts will usually
involve conditions such as P(B|A) > P(B|¬A) for cause A and effect B.
Notice this is an atemporal condition. Also in reponse to Mike - the
relation between A and B given is a definitive causal relation)

>
> If a billiard ball A hits another B and B moves what we perceive is A
> hitting and B moving. We see this each time and every time. But we never
> perceive a necessary connection. We supply that by supposition. We
> hypothesize, in the case of the billiard balls, an energy transfer. We
> presume the conservation of momentum. Neither the conservation of
> momentum nor the conservation of energy are necessary a priori
> principles. We assume them because of our experience.

There have been many explanations of cause in terms of physics, for example
energy transfer as you said others such as microscopic interaction etc etc,
but I must point out that these cannnot provide the truth conditions for
propositions such as 'A causes B' for example possible worlds which are
nevertheless causal but in which the law of conservation of energy does not
hold, and hence cannot codify what cause means.

It is important to keep in mind here what we mean by causal. Yes indeed,
the world is causal in the sense that we have certain repeatable events of a
certain type after which another type of event occurs *more often than
not*. Now, statistically, this means that occurences of the first type of
event raise the probability of occurences of the second type of event,
and hence we can establish a causal relation, we can say the first event
causes the second event purely from the definition. This applies to quantum
mechanics as well, so in this sense quantum mechanics is causal as well, in
the sense that partical interactions have wave functions with probability
peaks at the most probable places. However, when people say QM isn't causal
they usually mean its not causally determined with inus conditions etc (this
is because in probabalistic black boxes inus conditions giving locations and
momentums of the particles just can't be given - and whether they're there
or not is metaphysical nonsense). We must remember that the world isn't
causally determined on the macroscopic level *either*, light switches are
especially designed not to fail randomly (although they occasionally do), so
flipping a light switch isn't a good example. A standard example is 'smoking
causes lung cancer'. This statement is true, nevertheless there are people
who smoke who haven't got lung cancer (and never will), moreover there are
people who have lung cancer but have never smoked. So in short causes are
not necessary and sufficient conditions for their effects.
Yours,
Andrew

>
> Bob Kolker
>
>

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