If everything that happens in the world ultimately comes down to the behavior of fundamental particles, it would seem that other entities, from cells to human beings, from currencies to financial markets, aren't really causing anything at all—that they are just shadows cast by patterns at the most fundamental level. But philosopher David Yates argues this conclusion is wrong. The whole affects the parts, and higher-level structures don't just describe what is happening at lower levels in more convenient terms—they actively shape what is possible. This means that chemists, biologists, psychologists, and economists aren't chasing shadows. They are studying structures that genuinely shape how the world unfolds.

In 1974, Jerry Fodor published a seminal paper titled ‘Special Sciences’, in which he argued for an intuitive and compelling picture of the relationship between fundamental physics and higher-level sciences such as biology, psychology and economics. Our world, according to Fodor, is arranged hierarchically, with fundamental physical particles at the bottom, combining to form molecules, which combine to form cells, which combine to form complex organisms, some of which have mental states, among them humans, who combine to form complex societies. The sciences are likewise arranged, with physics at the bottom, followed by chemistry, biology, physiology, neuroscience, psychology, sociology and economics. Now it is vanishingly unlikely, says Fodor, that things that share e.g. psychological or economic properties, also share some property specifiable in the language of physics or other lower-level sciences. There are indefinitely many ways in which a financial transaction might be physically implemented; and what are the chances that two different people, both thinking the thought that they ought to reduce international travel due to the climate crisis, are in exactly the same brain state?

Special sciences enable us to discover distinctive higher-level laws that are typically not expressible in the languages of the sciences below. To make the point vivid, consider a very high-level science, economics, and consider the following generalization: during a recession, the banks will lower interest rates to increase public spending and stimulate the economy. Suppose it’s an economic law that decreasing interest rates causes a rise in public spending, which in turn stimulates economic growth. What does a rise in interest rates look like, at the quantum physical level? Or an increase in spending? Or economic growth? Economic events like recessions or currency transactions will not have anything at all in common at the level of quantum physics, and so economic laws are invisible at that level. It isn’t just that biologists, psychologists and economists can’t get the funding to build particle accelerators and space telescopes; even if they could, they wouldn’t have any use for such things. The events, processes and laws that interest them simply don’t belong to physics, and must be studied within their own domains, using the characteristic techniques of their particular sciences.

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Even if all forces are fundamental physical forces, there is still, I claim, plenty of causal work for higher level states to do.

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