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The Anthropic Principle states that the fundamental physics of the universe must allow the possibility of conscious life in the universe - as that is an observable fact.

It's often qualified as pseudo-science. The pseudo qualifier is pejorative. Yet it certainly sets bounds on what the fundamental constants of physics must lie in - if we take the machinary of the Standard Model as fixed but the constnts variable.

Is it falsifiable which is Poppers criterion for a scientific theory. If not, then what actually is its philosophical status if it lies outside the realm of falsifiable theories? Can it still count as scientific and objective as physics proper - as it has a direct bearing on the parameters that the standard model can take?

EDIT

As evidence that the Anthopic Principle is taken seriously in science with as Schellekin notes 'palpable reluctance' the following quote may help:

From the abstract of Schellekens paper Life at the interface of Particle Physics & String Theory, an Invited contribution to Reviews of Modern Physics

Meanwhile there has been increasing evidence that the seemingly ideal candidate for answering these questions, String Theory, gives an answer few people initially expected: a huge "landscape" of possibilities, that can be realized in a multiverse and populated by eternal inflation. At the interface of "bottom-up" and "top-down" physics, a discussion of anthropic arguments becomes unavoidable.

and then in the main body of the text

ANTHROPIC LANDSCAPES The idea that our own existence might bias our observations has never been popular in modern science, but especially during the last forty years a number of intriguing facts have led scientists from several areas of particle physics, astrophysics and cosmology in that direction, often with palpable reluctance. Examples are Dirac's large number hypothesis in astrophysics (Carr and Rees, 1979; Carter, 1974), chaotic inflation (Linde, 1986b), quantum cosmology (Vilenkin, 1986), the cosmological constant (Barrow and Tipler, 1986; Davies and Unwin, 1981;Weinberg, 1987), the weak scale in the Standard Model(Agrawal et al., 1998b), quark and lepton masses in the Standard Model (Hogan, 2000), the Standard Model in string theory (Schellekens, 1998) and the cosmological constant in string theory (Bousso and Polchinski, 2000;Susskind, 2003).

he also says

The rest of this section does not depend on the details of the string landscape, except that at one point we will assume discreteness. However, the existence of some kind of landscape in some fundamental theory is a prerequisite. Without that, all anthropic arguments lose there scientific credibility

This is probably a little more negative than it should be, as it sounds as though if the Anthropic Principle would be of no interest & vacuous if a possible mechanism hadn't been identified. after it is undeniable that the Anthopic argument was made well before the advent of String Theory. That the landscape in string theory offers a mechanism makes the argument concrete & scientific, but by the same token one should then assert that the argument was of philosophical interest before this possibility announced itself.

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    There's no question. – iphigenie May 5 '13 at 8:51
  • @iphigenie: is this better? – Mozibur Ullah May 5 '13 at 9:20
  • Related/further reading: This website goes with the book by Bostrom. – user3164 May 5 '13 at 9:52
  • @Gugg: observation selection does apply. The standard model may not be the only way to construct a universe. There may be other models which are not simply deformations through parameters. (I did mention this in my original phrasing of the question). But one has to close off possibities in some manner - and this is the usual presentation. – Mozibur Ullah May 5 '13 at 10:38
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    Perhaps it is falsifiable: Is there indeed empirical proof of the existence of 'conscious life in the universe'?! – Vector May 5 '13 at 22:52
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Not every aspect of reasoning employed during the scientific process has to be "falsifiable". For example, physicists routinely employ mathematics that assumes mathematical induction, which isn't a falsifiable axiom (and indeed it could be false if we're in a simulation, as all inductions would ultimately fail due to the equivalent of a segfault or stack overflow). This is okay--you only need to be able to falsify your hypotheses, not every step of reasoning that leads you to them. If you don't end up somewhere falsifiable, you need to keep reasoning or postulating until you do end up with something falsifiable.

The Anthropic Principle isn't a hypothesis. It's just some reasoning that reminds you of which hypotheses already contradict something that you are (almost completely) sure that you know. Any hypothesis that assumes there is no conscious life is wrong because it's already been falsified by our existence! Very handy, that. One could make an "oxygenic principle" also that any laws of physics that are incompatible with the existence of oxygen can also be summarily dismissed.

So there's really nothing to see here. It's got an exciting name, but when it comes to actually reasoning about science, there's nothing particularly remarkable about this as opposed to any other statement that we shouldn't favor theories that make impossible something that is obviously the case. It doesn't explain anything. It's not causal. It just reminds you when you've made a really stupid mistake, like if you're calculating how far it will be from you to New York and you calculate -470 miles. You don't have any idea where you went wrong, but it's blatantly obvious that you made a calculation error somewhere along the way.

Any use of the anthropic principle beyond this is not scientific. (It does get used; people enjoy speculating. If you are interested in science, it is a good idea to ignore these speculations.)

  • Poppers notion of falsifiability applies to scientific rather than mathematical theories. I agree that the Anthropic principle is not a hypothesis; it is in fact an observation. Observations are part of empirical science as well as Natural Philosophy. The point is that the fundamental constants are taken as constants. But there are hypotheses that this may not in fact be true. For example there are theories that do allow a variable value of the speed of light. If one constant can change, perhaps others can. – Mozibur Ullah May 7 '13 at 5:16
  • It is an observation that life exists. One then has to explain how the constants have converged to allow for life. Of course this is speculation. But then again String Theory is speculation but it has proven extremely fruitful. – Mozibur Ullah May 7 '13 at 5:22
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    @MoziburUllah - The anthropic principle is not an observation. That we exist is the observation. There's no requirement to make a principle out of it. There is also no requirement to take the strong form of the anthropic principle (i.e. that it must have happened this way); that we are the lucky ones who are observing a universe consistent with consciousness is entirely possible also. And since we don't understand the mapping from physical laws to consciousness, even the strong principle doesn't constrain very much. – Rex Kerr May 7 '13 at 14:11
  • Exactly how we divide scientific theories from their compliment, I'm not sure, but here is at least another proposal for a non-falsifiable scientific claim: All claims about the physical world should be falsifiable. – Addem Jul 3 '13 at 19:22
  • I find this to be quite unclear. Perhaps one or two valid uses of the AP and one or two invalid uses would help illustrate? – labreuer Feb 16 '14 at 6:35
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Arguments from string theory probably shouldn't hold too much ground, because there is still intense debate over whether or not string theory is falsifiable (for exactly the same reasons that string theorists use anthropic reasoning; i.e., there is a inconceivably vast landscape of possible solutions to string theory).

However, in most areas of physics the anthropic principle is falsifiable. For example, for a time there was a popular idea that the universe was a great ball of gas in thermal equilibrium, and the universe that we observe is just a freak fluctuation in the positions of this gas. Every fluctuation has a probability of showing up, so eventually we should see every fluctuation; the only question is, how did we wind up in this one? Anthropic principle!

However, this is not only falsifiable, but false. The reason is that the probability of two massive bodies fluctuating into existence is the product of their individual probabilities of fluctuating into existence. So the probability that the earth would fluctuate into existence is massively more probable than the earth would fluctuate into existence along with all the stars and galaxies that we observe. (I mean, like 10^googol times as probable.) It's even more probable that only you would pop into existence, or only your brain would pop into existence.

The moral of the story is: the hypothesis "we are observers, therefore we must be in a part of the universe('s history) amenable to such observers" makes a very strong prediction: that the universe would be nothing at all like what we observe it to be. Boom. Falsified.

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Yes it's falsifiable, if a deeper theory shows there isn't a landscape of variation of fundamental constants. Then other conditions than the presence of observers would be acting.

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