Archive for Immanuel Kant

Das Kapital [not a book review]

Posted in Statistics with tags , , , , , , , , , , , on August 18, 2017 by xi'an

A rather bland article by Gareth Stedman Jones in Nature reminded me that the first volume of Karl Marx’ Das Kapital is 150 years old this year. Which makes it appear quite close in historical terms [just before the Franco-German war of 1870] and rather remote in scientific terms. I remember going painstakingly through the books in 1982 and 1983, mostly during weekly train trips between Paris and Caen, and not getting much out of it! Even with the help of a cartoon introduction I had received as a 1982 Xmas gift! I had no difficulty in reading the text per se, as opposed to my attempt of Kant’s Critique of Pure Reason the previous summer [along with the other attempt to windsurf!], as the discourse was definitely grounded in economics and not in philosophy. But the heavy prose did not deliver a convincing theory of the evolution of capitalism [and of its ineluctable demise]. While the fundamental argument of workers’ labour being an essential balance to investors’ capital for profitable production was clearly if extensively stated, the extrapolations on diminishing profits associated with decreasing labour input [and the resulting collapse] were murkier and sounded more ideological than scientific. Not that I claim any competence in the matter: my attempts at getting the concepts behind Marxist economics stopped at this point and I have not been seriously thinking about it since! But it still seems to me that the theory did age very well, missing the increasing power of financial agents in running companies. And of course [unsurprisingly] the numerical revolution and its impact on the (des)organisation of work and the disintegration of proletariat as Marx envisioned it. For instance turning former workers into forced and poor entrepreneurs (Uber, anyone?!). Not that the working conditions are particularly rosy for many, from a scarsity of low-skill jobs, to a nurtured competition between workers for existing jobs (leading to extremes like the scandalous zero hour contracts!), to minimum wages turned useless by the fragmentation of the working space and the explosion of housing costs in major cities, to the hopelessness of social democracies to get back some leverage on international companies…

RSS Read Paper

Posted in Books, pictures, Statistics, Travel, University life with tags , , , , , , , , on April 17, 2017 by xi'an

I had not attended a Read Paper session at the Royal Statistical Society in Errol Street for quite a while and hence it was quite a treat to be back there, especially as a seconder of the vote of thanks for the paper of Andrew Gelman and Christian Hennig. (I realised at this occasion that I had always been invited as a seconder, who in the tradition of the Read Papers is expected to be more critical of the paper. When I mentioned that to a friend, he replied they knew me well!) Listening to Andrew (with no slide) and Christian made me think further about the foundations of statistics and the reasons why we proceed as we do. In particular about the meaning and usages of a statistical model. Which is only useful (in the all models are wrong meme) if the purpose of the statistical analysis is completely defined. Searching for the truth does not sound good enough. And this brings us back full circle to decision theory in my opinion, which should be part of the whole picture and the virtues of openness, transparency and communication.

During his talk, Christian mentioned outliers as a delicate issue in modelling and I found this was a great example of a notion with no objective meaning, in that it is only defined in terms of or against a model, in that it addresses the case of observations not fitting a model instead of a model not fitting some observations, hence as much a case of incomplete (lazy?) modelling as an issue of difficult inference. And a discussant (whose Flemish name I alas do not remember) came with the slide below of an etymological reminder that originally (as in Aristotle) the meaning of objectivity and subjectivity were inverted, in that the later meant about the intrinsic nature of the object, while the former was about the perception of this object. It is only in the modern (?) era that Immanuel Kant reverted the meanings…Last thing, I plan to arXiv my discussions, so feel free to send me yours to add to the arXiv document. And make sure to spread the word about this discussion paper to all O-Bayesians as they should feel concerned about this debate!

Kant, Platon, Bayes, & Le Monde…

Posted in Books, Statistics, University life with tags , , , , , , , , , , , , on July 2, 2012 by xi'an

In the weekend edition of Le Monde I bought when getting out of my plane back from Osaka, and ISBA 2012!, the science leaflet has a (weekly) tribune by a physicist called Marco Zito that discussed this time of the differences between frequentist and Bayesian confidence intervals. While it is nice to see this opposition debated in a general audience daily like Le Monde, I am not sure the tribune will bring enough light to help to the newcomer to reach an opinion about the difference! (The previous tribune considering Bayesian statistics was certainly more to my taste!)

Since I cannot find a link to the paper, let me sum up: the core of the tribune is to wonder what does 90% in 90% confidence interval mean? The Bayesian version sounds ridiculous since “there is a single true value of [the parameter] M and it is either in the interval or not” [my translation]. The physicist then goes into stating that the probability is in fact “subjective. It measures the degree of conviction of the scientists, given the data, for M to be in the interval. If those scientists were aware of another measure, they would use another interval” [my translation]. Darn… so many misrepresentations in so few words! First, as a Bayesian, I most often consider there is a true value for the parameter associated with a dataset but I still use a prior and a posterior that are not point masses, without being incoherent, simply because the posterior only summarizes what I know about the  parameter, but is obviously not a property of the true parameter. Second, the fact that the interval changes with the measure has nothing to do with being Bayesians. A frequentist would also change her/his interval with other measures…Third, the Bayesian “confidence” interval is but a tiny (and reductive) part of the inference one can draw from the posterior distribution.

From this delicate start, things do not improve in the tribune: the frequentist approach is objective and not contested by Marco Zito, as it sounds eminently logical. Kant is associated with Bayes and Platon with the frequentist approach, “religious wars” are mentioned about both perspectives debating endlessly about the validity of their interpretation (is this truly the case? In the few cosmology papers I modestly contributed to, referees’ reports never objected to the Bayesian approach…) The conclusion makes one wonders what is the overall point of this tribune: superficial philosophy (“the debate keeps going on and this makes sense since it deals with the very nature of research: can we know and speak of the world per se or is it forever hidden to us? (…) This is why doubt and even distrust apply about every scientific result and also in other settings.”) or criticism of statistics (“science (or art) of interpreting results from an experiment”)? (And to preamp a foreseeable question: no, I am not writing to the journal this time!)

Can we prove scientific hypotheses?

Posted in Kids, Statistics with tags , , , , on June 17, 2011 by xi'an

Today was the first day of the French Baccalauréat, the comprehensive exam at the end of high school French students must get to enter higher education. Customarily, the first day of the exam starts with the philosophy composition and one of the questions this year was “Can we prove scientific hypotheses?“. This is both a nice question and a hard topic for teenagers! For instance, I do not think they have been exposed to Karl Popper as part of their program. Maybe not even Immanuel Kant. And certainly not Poincaré’s La science et l’hypothèse. (I do remember reading Feyerabend’s Against Method on my own, but this may have been the year after baccalauréat… And I definitely tried Kant as beach reading in Corsica only two years later!) So the most likely answer from students exposed to experimental methods (and not at all to statistics) will be a cautious yes. Even the poor correction provided by Philomag concludes this way (despite quoting Popper and Kant). A funny thing is that this question was part of the literary section, not of the scientific section! In the science section, the question was not unrelated “Can we be right against the facts?” but was certainly harder to argue. (My son took instead a cautionary approach by discussing a text from Pascal. I would have rather picked the above or “Does culture de-nature man?“)