# Axiom of Causality?

1. Dec 12, 2008

### Crazy Tosser

Do you agree with this?
http://en.wikipedia.org/wiki/Axiom_of_Causality

"The Axiom of Causality is the proposition that everything in the universe has a cause and is thus an effect of that cause. This means that if a given event occurs, then this is the result of a previous, related event. If an object is in a certain state, then it is in that state as a result of another object interacting with it previously. For example, if a baseball is moving through the air, it must be moving this way because of a previous interaction with another object, such as being hit by a baseball bat."

I personally don't think this is absolutely correct, but I'd like to hear some other opinions.

2. Dec 12, 2008

### Tac-Tics

In the general meaning given, this smells like philosophy. Definitely not the soothing aroma of science or math.

What constitutes an event? What is an effect? If they have to be related, what is the nature of their relation? This "axiom" specifies none of these things. It's a useless statement.

The section of the article about energy in a magnetic field was written by someone who doesn't understand electrodynamics.

The issue about quantum mechanics having an inner mechanism is more interesting than the rest of the article for these forums, but it's still a matter of philosophy.

3. Dec 12, 2008

### franznietzsche

Well, this is the philosophy subforum.

In philosophy of science 'event' is generally taken to mean an interaction. Effect is the outcome of the interaction. The axiom is far from useless.

Actually the entire article sounds like it was written by someone who doesn't know what they were talking about, including the part about quantum mechanics. Quantum mechanics violates the principle of local reality, NOT causality. They are different principles.

An effect is an outcome of an interaction. Interactions in quantum mechanics are called measurements. Say we measure the position of a particle at two different times $$t_a$$ and $$t_b$$. Assuming no external interference in the experiment, at $$t_a$$ the particle will have a certain wavefunction $$\Psi$$, which we have measured in position space. The wavefunction will evolve from $$t_a$$ to $$t_b$$ in a DETERMINISTIC fashion that we can calculate. At $$t_{b-1}$$ the particle has a known wavefunction that tells us the probability of finding the particle at a given point. If we measure its position (thus interacting) the wavefunction collapses to a particular position eigen-state (we change the state of the particle causing an effect) which tells us the wavefunction at $$t_b$$. If we do this many times, we find that the overall numbers match the probability from the deterministic wavefunction.

See, in quantum mechanics the WAVEFUNCTION is what is affected by interactions, and the wavefunction IS deterministic and causal. Which eigenstate a particular measurement gets is not, but the wavefunction is.

4. Dec 12, 2008

### Tac-Tics

It was moved out of the general physics subforum, I believe. I didn't realize it was moved until after I posted.

5. Dec 12, 2008

### WaveJumper

Huh? What causes the observed "spontaneous creation and annihilation of particles in vacuum" also known as "vacuum fluctuations"?

Many physicists believe the universe in which you are writing the above statement was created without God by use of these UNcaused vacuum fluctuations.

6. Dec 12, 2008

### franznietzsche

That is an entirely separate phenomenon from what I was talking about.

This is such a gross oversimplification that it is beyond description.

Quantum mechanics is a theory in which abstract operators act on an abstract state space. The evolution of the wavefunction (which exists in Hilbert space) is perfectly deterministic and causal.

As for systems where the number of particles is not constant there are several possibilities. Generally there are situations where you have a multi-particle system in a state that is not an eigenstate of $$\hat N$$. Even in these situations however, the evolution of the quantum state of the system is deterministic and causal.

7. Dec 18, 2008

### KAckermann

If you walk into a bar and see a que ball at rest on a pool table, what indications do you have on how it arrived at that state?

Not all information is preserved.

8. Feb 6, 2009

### Lord Ping

I think a fairly innocuous version of that "axiom" is the claim that:

"The state of the universe at time t in some sense depends on the state of the universe at some earlier time t-d."

You'd have to be crazy to deny this much. The fact that I'm at my desk now in some sense depends on the fact that I was at my desk one second ago. If I'd been on Mars one second ago, I would not be at my desk now.

Naturally one then wonders what the nature of this "dependence" is.

There is "dependence" in so far as the state of the universe at time t is constrained by the state of the universe at t-d and the laws of physics. It cannot be the case that I was on Mars one second ago and am at my desk now, because the laws of physics preclude such a bizarre succession of events.

But it is interesting that this notion of lawful dependence does not even come close to capturing all our commonsense intuitions about causal dependence. To say that "Hitler's rise to power caused WW2" is certainly not the same as saying that the rise of Hitler plus the laws of physics made WW2 inevitable.

An enormous and fascinating body of philosophical literature has thus arisen, trying to work out what on earth our everyday notion of causal dependence actually means.

9. Feb 7, 2009

### Moridin

Causality can be interpreted as objects acting in accordance with their identity. If such is the case, uncased events does not actually violate the principle of causality, since not having a precedent event in time is perfectly in order with their identity.

10. Feb 11, 2009

### JoeDawg

This relates to the more generalized Problem of Induction, first clearly defined by Hume.
http://en.wikipedia.org/wiki/Problem_of_induction

Causality is basically an unjustified assumption, one that can't be justified by experience or rational argument. What we experience, what science mainly deals with, is better referred to as correlations. Some correlations are more consistent than others, mind you, which is where common sense notions of causality come in. You don't have to deny causality to recognize its an assumption. Its simply a limitation on rational and empircal knowledge.

For instance, when playing billards, we can observe the white ball in motion, then it stops moving, and another ball starts moving.(We don't observe the white ball CAUSING the second ball to move.) We just see a correlation in movement. This is the observation. The two motions correlate and based on consistency in experience we develop a theory of causality. The problem of induction however prevents any justification beyond the fact that causality is a 'useful belief' about the universe. Hume referred to our reliance on inductive reasoning as a habit. Induction being the reasoning from specific to general. We can do this via 'causation' but also via observed to unobserved phenomena.

Its been a problem in the philosophy of science ever since Hume.

Last edited: Feb 11, 2009
11. Feb 11, 2009

### The Dagda

Such an axiom is the reason the ontological question fails, if everything has a cause then that which is caused must of had a cause back to an infinite regress. This means of course that in terms of logic the ontological question and any other causality question fails by default.

http://en.wikipedia.org/wiki/Infinite_regress

Let's say the cause of the Universe is x, and that cause followed from x0, then what did that cause follow from? What plagues the human mind is something Kant summed up rather well, just because you cannot grasp something from nothing, or infinity does not mean they aren't useful terms and in the case of the former it also doesn't mean they cannot happen. If you can't reconcile your fragile mind with the fact that your fragile mind is a result of causality, then how do you hope to understand a cause without a cause and even if you could wouldn't you reject it arbitrarily? Suffice to say the axiom of causality is worthless logically in that it requires an a priori assumption that no one is able to verify or make sense of and for all we know is worthless.

Last edited: Feb 11, 2009
12. Feb 12, 2009

### Werg22

I wonder what that's supposed to mean. If anything, science and math provide the most perplexing philosophical questions.

13. Feb 12, 2009

### meopemuk

To me this means that the result of a particular measurement (which is a real physical event) is random, unpredictable in principle, and therefore does not have a cause.

14. Feb 16, 2009

### Max™

Our perception of causality is biased by our limited perception of time, by the illusory importance we attribute to the perceived Now.

Quantum effects could alternatively be described as local and retrocausal, akin to the Bohmian interpretation.

I think the only definition of causality which could be accepted would refer to events which are separated by very short durations and distances, with no implied preference for one direction or another.