1. Is String Theory Scientific? Keizo.Matsubara@filosofi.uu.se and Lars-Goran.Johansson@filosofi.uu.se

2. A quote from the works of Richard P. Feynman “Philosophers say a great deal about what is absolutely necessary for science, and it is always, so far as one can see, rather naïve, and probably wrong.” “Philosophers say a great deal about what is absolutely necessary for science, and it is always, so far as one can see, rather naïve, and probably wrong.” The Feynman Lectures on Physics. Ch. 1, Vol. I The Feynman Lectures on Physics. Ch. 1, Vol. I

3. There is no real consensus among philosophers Philosophers disagree about almost everything! Philosophers disagree about almost everything! Our business as philosophers is to question presuppositions usually made by scientists, philosophers and people in general. Our business as philosophers is to question presuppositions usually made by scientists, philosophers and people in general. When one criticizes philosophy in general it is very hard to avoid formulating a new philosophical position. When one criticizes philosophy in general it is very hard to avoid formulating a new philosophical position.

4. A few comments on the discussion A few comments on the discussion There have been opponents to string theory for a long time. Many experimentalists have been skeptical. Criticism have also been expressed by philosophers of science. There have been opponents to string theory for a long time. Many experimentalists have been skeptical. Criticism have also been expressed by philosophers of science. The books by Smolin and Woit caused further debate. The books by Smolin and Woit caused further debate. The discussion has partly been too simplistic and held as if though Popper was the only relevant philosopher to discuss. The discussion has partly been too simplistic and held as if though Popper was the only relevant philosopher to discuss.

5. Many perspectives We will look at how string theory would be evaluated according to the following different perspectives: Logical Positivists Logical Positivists Popper Popper Kuhn Kuhn Lakatos Lakatos Feyerabend Feyerabend Different answers will be given.

6. Logical positivists The Vienna circle The Vienna circle Empiricist views on science Empiricist views on science Verification criterion for meaning Verification criterion for meaning Instrumentalist Instrumentalist Antimetaphysical Antimetaphysical Stressed the use of strict logical methods Stressed the use of strict logical methods Inductive method Inductive method

7. Logical positivism and string theory String theory would be considered strictly speaking meaningless since it does not connect to experiment. String theory would be considered strictly speaking meaningless since it does not connect to experiment. Since they are basically supporting induction as the basis for scientific method they conceived of the development of a theory coming after the data. Since they are basically supporting induction as the basis for scientific method they conceived of the development of a theory coming after the data. The “work in progress”- argument can be made, but that would be questionable given the assumptions. The “work in progress”- argument can be made, but that would be questionable given the assumptions.

8. Note There are really no philosophers who defend traditional logical positivism. There are really no philosophers who defend traditional logical positivism. Some of their views, however, remain influential to the way scientists and philosophers think about science. Some of their views, however, remain influential to the way scientists and philosophers think about science. Internal problems with the position and severe criticism has destroyed it. Internal problems with the position and severe criticism has destroyed it.

9. Popper Hypothetico-deductive method. Hypothetico-deductive method. A scientific theory needs to be falsifiable. A scientific theory needs to be falsifiable. A theory could be meaningful although not falsifiable, thus not scientific. A theory could be meaningful although not falsifiable, thus not scientific. Popper have nothing against speculations and metaphysical assumptions in principle, but it is only when a theory is put into a falsifiable formulation that a theory is scientific. Popper have nothing against speculations and metaphysical assumptions in principle, but it is only when a theory is put into a falsifiable formulation that a theory is scientific.

10. Hypothetico-deductive method H=hypothesis E=empirical consequence H  E H  E Not E E ______ ------------ H falsified H supported /corroborated

11. Popperazzi? Susskind mentions the Feynman statement, quoted earlier, which expressed a less than favorable description of philosophers. He clearly implies that the criticism directed towards philosophers in general applied to Popper in particular. Susskind mentions the Feynman statement, quoted earlier, which expressed a less than favorable description of philosophers. He clearly implies that the criticism directed towards philosophers in general applied to Popper in particular. But what was Feynman’s own views on scientific method?

12. Scientific Method according to Feynman “In general we look for a new law by the following process. First we guess it. Then we compute the consequences of the guess to see what would be implied if this law that we guessed is right. Then we compare the result of the computation to nature, with experiment or experience, compare it directly with observation, to see if it works. If it disagrees with experiment it is wrong. In that simple statement is the key to science. It does not make any difference how beautiful your guess is. It does not make any difference how smart you are, who made the guess or what his name is – if it disagrees with experiment it is wrong.”

13. Scientific Method according to Feynman, continued “You can see of course, that with this method we can attempt to disprove any definite theory. If we have a definite theory, a real guess, from which we can conveniently compute consequences which can be compared with experiment then in principle we can get rid of any theory. There is always the possibility of proving a definite theory wrong; but notice that we can never prove it right.”

14. Scientific Method according to Feynman, continued “Suppose that you invent a guess, calculate the consequences, and discover every time that the consequences you have calculated agree with experiment. The theory is then right? No, it is simply not proved wrong. In the future you could compute a wider range of consequences, there could be a wider range of experiments and you might then discover that the thing is wrong” The Character of Physical Law pp. 156-158

15. What does this show? Not very much; only that Susskind can not claim to have an ally in Feynman when defending string theory against the “Popperazzi”. Not very much; only that Susskind can not claim to have an ally in Feynman when defending string theory against the “Popperazzi”. It should also be noted that Feynman was highly critical of string theory, to a large extent for Popperian reasons. Since Feynman died in 1988 all he said regarding string theory refers to the theory before that but it is hard to think that he would have changed his assessment. It should also be noted that Feynman was highly critical of string theory, to a large extent for Popperian reasons. Since Feynman died in 1988 all he said regarding string theory refers to the theory before that but it is hard to think that he would have changed his assessment.

16. A Popperian evaluation of String theory String theory is not meaningless String theory is not meaningless String theory is not yet falsifiable and is hence not yet a scientific theory. String theory is not yet falsifiable and is hence not yet a scientific theory. The “work in progress”- argument can more plausibly be used here to defend research in string theory as legitimate, as long as one admits that one has not yet succeeded in formulating a scientific theory. The “work in progress”- argument can more plausibly be used here to defend research in string theory as legitimate, as long as one admits that one has not yet succeeded in formulating a scientific theory. Comparison should be made with the examples Popper criticized viz. Psychoanalysis and Marxism. The situation is NOT the same as the one for string theory… Comparison should be made with the examples Popper criticized viz. Psychoanalysis and Marxism. The situation is NOT the same as the one for string theory…

17. There are problems with Popper’s views on science! There are problems with Popper’s views on science! To derive consequences from a hypothesis one typically need to use a host of different auxiliary assumptions and when things do not turn out as expected one can blame the auxiliary assumptions. To derive consequences from a hypothesis one typically need to use a host of different auxiliary assumptions and when things do not turn out as expected one can blame the auxiliary assumptions. When modifying auxiliary assumptions one is supposed to avoid modifications that are ad hoc. When modifying auxiliary assumptions one is supposed to avoid modifications that are ad hoc. It is however not at all easy to define ad hocness clearly. It is however not at all easy to define ad hocness clearly.

18. Kuhn Paradigms Paradigms Normal Science vs. Revolutionary Science Normal Science vs. Revolutionary Science Puzzle Solving Puzzle Solving Incommensurability Incommensurability

19. Normal science in string theory? String theory is clearly so well defined so that puzzles and problems can be formulated and solved within the framework. The puzzles are however only of a theoretical nature and does that really count? String theory is clearly so well defined so that puzzles and problems can be formulated and solved within the framework. The puzzles are however only of a theoretical nature and does that really count? String theory has many of the features expected by a mature science but since it does not yet solve puzzles connected with experiment it is not clear how Kuhn would have described that. String theory has many of the features expected by a mature science but since it does not yet solve puzzles connected with experiment it is not clear how Kuhn would have described that.

20. A Kuhnian evaluation of string theory It is not completely clear whether or not Kuhn’s analysis applies. It is not completely clear whether or not Kuhn’s analysis applies. String theory has some features of normal science. String theory has some features of normal science. Kuhn’s position is largely descriptive and not particularly normative. A point might be made that the dominance of a paradigm might have occurred even when there are no experiments, and the processes behind this might be more or less the same… Kuhn’s position is largely descriptive and not particularly normative. A point might be made that the dominance of a paradigm might have occurred even when there are no experiments, and the processes behind this might be more or less the same…

21. Lakatos Lakatos’ position is to some extent similar to Kuhn’s but he denies incommensurability. Lakatos’ position is to some extent similar to Kuhn’s but he denies incommensurability. He uses the term “research program” instead of “paradigm” but what they refer to is roughly similar. He uses the term “research program” instead of “paradigm” but what they refer to is roughly similar. A research program have basic assumptions in the “hard core” these should not be questioned within the program. If you abandon them you have abandoned the program. A research program have basic assumptions in the “hard core” these should not be questioned within the program. If you abandon them you have abandoned the program. Lakatos basic norm is that it is rational to leave a degenerate program in favor of a progressive one. (This is not a strict rule…but rather a rule of thumb.) Lakatos basic norm is that it is rational to leave a degenerate program in favor of a progressive one. (This is not a strict rule…but rather a rule of thumb.)

22. A Lakatosian evaluation of string theory String theory could be considered theoretically progressive but not progressive in the way Lakatos intended, since it is only solving theoretical puzzles. String theory could be considered theoretically progressive but not progressive in the way Lakatos intended, since it is only solving theoretical puzzles. One should not abandon a research program unless there is a better alternative. One should not abandon a research program unless there is a better alternative. String Theory roughly fits into Lakatos conception of a scientific research program and can thus be considered scientific. String Theory roughly fits into Lakatos conception of a scientific research program and can thus be considered scientific.

23. A new norm? According to a Lakatosian view String Theory would be respectable. But so would other approaches. If a research program becomes empirically progressive it would be rational to focus on that. But when programs that are only theoretically progressive to various degrees are competing which strategy would be best to use? Is there a risk with having a dominant program such as string theory? According to a Lakatosian view String Theory would be respectable. But so would other approaches. If a research program becomes empirically progressive it would be rational to focus on that. But when programs that are only theoretically progressive to various degrees are competing which strategy would be best to use? Is there a risk with having a dominant program such as string theory?

24. Another quote from Feynman “ If every individual student follows the same current fashion in expressing and thinking about [the generally understood areas], then the variety of hypotheses being generated to understand [the still open problems] is limited. Perhaps rightly so, for possibly the chance is high the truth lies in the fashionable direction. But [if] it is another direction … who will find it? ” From the Nobel Lecture 1965.

25. Feyerabend Since no strict effective rules can be specified that once and for all define scientific method there really is no scientific method. Since no strict effective rules can be specified that once and for all define scientific method there really is no scientific method. “Anything goes!”. What did he mean? “Anything goes!”. What did he mean? Feyerabend have said things to the effect that there is no real difference between science compared with voodoo, astrology or any other theories or worldviews. Feyerabend have said things to the effect that there is no real difference between science compared with voodoo, astrology or any other theories or worldviews.

26. A Feyerabendian evaluation of String Theory Since Feyerabend abandons the question to even try to find criteria for scientific method he basically allows anything and would of course also accept string theory. Since Feyerabend abandons the question to even try to find criteria for scientific method he basically allows anything and would of course also accept string theory. Of course Feyerabend’s radical position is probably not acceptable to most scientists. Of course Feyerabend’s radical position is probably not acceptable to most scientists.

27. Should philosophers dictate scientific method? The point is not that philosophers dictate questions of method. What methods are applied is decided by the practicing scientists but there is a constant debate on the issues and the philosophers are participants in this debate. The point is not that philosophers dictate questions of method. What methods are applied is decided by the practicing scientists but there is a constant debate on the issues and the philosophers are participants in this debate. We believe that it is beneficial for scientists to be at least aware of how these problems are discussed and the different philosophical position there are. We believe that it is beneficial for scientists to be at least aware of how these problems are discussed and the different philosophical position there are.

28. Conclusions: Is String Theory Scientific? Logical Positivism : No, but… Logical Positivism : No, but… Popper : Not yet, but… Popper : Not yet, but… Kuhn : Well maybe, but… Kuhn : Well maybe, but… Lakatos : Yes, but… Lakatos : Yes, but… Feyerabend : Who cares?! Feyerabend : Who cares?!