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Video: Laws of nature and explanation
Duration: 00:24:15
Date: 23-05-1973
Professor Alexandrova is Professor in Philosophy of Science in the Department of History and Philosophy of Science, University of Cambridge
Image : Professor Anna Alexandrova
Date: 2021

Laws of Nature

In 1973 three philosophers sat down to talk about laws of nature. They were Richard Braithwaite, by then retired as the Knightbridge Professor of Moral Philosophy and a mainstay of Cambridge philosophy for much of twentieth century; Kenneth Baublys, a young lecturer from Lancaster; and Oswald Hanfling of the Open University as the chair. Braithwaite’s book Scientific Explanation: A Study of the Function of Theory, Probability and Law in Science (1953) is the focal point and he duly plays the role of the grand man. Baublys is the earnest and a very nervous critic, navigating the challenge of posing objections to the famous professor. Hanfling directs his caring attention to the viewers studying this unit of the course at home, while deftly lowering the temperature of the interaction between Braithwaite and Baublys.
The immediate impression is of a stilted scene from a different age. There are the combovers, the lowtech special effects, the absence of women even in the language and the examples. But if you look past these, you witness a conversation that is perfectly intelligible both in style and in content.
The three men model to their audience what they see as a productive conversation in the tradition of Analytic Philosophy. It starts with the text, hence the helpful quotations on the screen read out by Hanfling, without which it would be impossible to understand Braithwaite’s intricate ideas. The goal of the conversation is to evaluate them on their soundness and validity, not on how evocative or wise they are. This is still how much of Analytic Philosophy is conducted. 
The substance of the conversation is also recognisable and I dare say current. The core distinction is between accidental and law-like generalisations and the core question is what makes a generalisation a law of nature. Is it a law because people treat this generalisation with due reverence or because the world makes it so? The former attitude is Hume’s, the latter Aristotle’s. This fundamental cleavage still divides philosophers of science and metaphysicians today. 
Baublys challenges Braithwaite on whether to be a law is to stand in the right deductive relation within a scientific theory. Doesn’t that imply there would be no laws if there weren’t scientists? Braithwaite stands firm – yes, laws are nothing without theories and theories are made by people. It is hard not to wonder if this comfort with subjectivity is an influence, not just of Hume, but also of his brilliant short-lived friend Frank Ramsey, who saw laws as just useful rules to plan our lives.
Today the technical term for such subjectivity is ‘agent-relativity’ – the idea that lawhood is relative to the use of these generalisations by people or animals. For Braithwaite this relativity arises out of the act of deduction from a theory, whereas today’s most popular accounts of laws locate relativity elsewhere. The American philosopher David Lewis, who was just getting started at the time of this conversation and whose theory of laws was going on to become the most influential, defined law as an axiom in a maximally economical system. Such a system is economical if it balances strength and simplicity better than any other. Simplicity is plausibly located in our language rather than in the world and if so lawhood would end up agent-relative. Another reason to think that it is us and not nature who decide if a generalisation is a law is the intimate connection of laws to causation. Often the reason why a universal generalisation ‘All As are Bs’ is a law is because As typically cause Bs. One popular way to think about causation is manipulability – an A causes a B because manipulating this A brings about a B. There is no manipulation without agents, so again they into the very heart of our theory of laws.
Not everybody agrees and there are many philosophers today who along with Baublys and Aristotle search for lawhood in the objective mind-independent, features of the world. This is the point of Nancy Cartwright's idea of capacities – causal powers inherent in objects around us that account for the generalisations we observe. She thinks metals would have the capacity to expand when heated even if we never arrived on the scene to observe, discover, or use this generalisation.
So all in all, neither Braithwaite’s own views, nor Baublys critique are outdated. We are still caught between them two.
Finally I want to honour the gracious chair of this discussion Oswald Hanfling. His lucid explanation of necessity and of counterfactual dependence is great pedagogy and it perfectly prepares the viewers for the debate to come. You couldn’t tell it from his accent, but Hanfling is a German Jew who came to England from Berlin on the Kindertransport and became a philosopher later in life thanks to Birkbeck’s evening classes. I hope that a story like his – of a refugee who becomes a professor thanks to accessible public higher education – is still possible in the UK today.
Anna Alexandrova
Anna Alexandrova is Professor in Philosophy of Science in the Department of History and Philosophy of Science, University of Cambridge.
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Debates and Discussions (page 8 of 14)