Historically, philosophers have looked at science and seen bold theories, couched in terms of universal laws, put to the test in crucial experiments that either refute or corroborate our theoretical hypotheses. They have seen a hierarchy, with physics as queen reigning over the lesser sciences, working down through chemistry, biology, and eventually to the social sciences. And they have extrapolated from their picture of science and its theories a picture of the world where, in the words of W. V. O. Quine, “nothing happens … not the flutter of an eyelid, not the flicker of a thought, without some redistribution of microphysical states”. This redistribution of microphysical states is held to be entirely governed by deterministic (or, in the case of quantum phenomena, indeterministic) physical laws. The resulting picture leaves little room for genuine agency, or even genuine explanations of occurrences beyond those that we might hope to be offered by fundamental physics. Given an initial configuration of microphysical states together with the physical laws governing their evolution, absolutely everything that happens occurs ultimately as a consequence of these initial conditions and laws.

When the philosopher Nancy Cartwright looks at science she sees quite a different picture. She challenges the image of scientists who simply produce bold theories and put these to experimental tests. She sees a rich and complex network of activities and methods; together they help us to develop the concepts in which our theories are formulated, build models and forge narratives with which to understand the world, and create the phenomena required to put these theories to work and to the test. Looking at experimental physics in particular, she takes as a case study the Stanford Gravity Probe B experiment, a $750 million project to test Einstein’s theory of general relativity using orbiting gyroscopes. The experiment was conceived in 1959–60 and work on designing the experiment began in 1962. The measurements were taken in 2004–05 and data analysis was published in 2011. The long delay from conception to execution was in part due to the time needed to prepare the technology to make the measurements possible. That included producing what are officially the world’s roundest objects: ping-pong-ball gyroscopic rotors of quartz so smooth that, if enlarged to the size of the earth, their largest mountain or deepest trench would be no more than 8ft. Why so smooth? Cartwright’s observation is that the laws of physics tell us how idealized objects – perfect spheres – should be expected to behave in the absence of external interference, not the messy objects of the ordinary world. To test these laws experimentally we have to make use of the resources of a vast range of scientific and engineering knowledge outside of “pure” physics in order to create environments – Cartwright describes them as “small worlds” – in which the laws of physics can be seen to work in their purest form. The interaction of practical and theoretical knowledge required to put our best physical theories to the test suggests to Cartwright that, far from all the sciences being “ultimately” just physics, not even physics is “just physics”.

Rather than being neat clockwork governed by fundamental physical laws, for Nancy Cartwright the world that scientists investigate is filled with untidy variety: an interacting range of powers and tendencies that combine in often unpredictable ways to produce the phenomena we observe. Does this mean that the “it’s all physics” picture offered by others is mistaken? As the author notes, both that dominant picture and her alternative are compatible with the data – scientific practices and their successes. But her engaging discussion offers a welcome counterpoint to a rather austere orthodoxy.

Mary Leng is Professor of Philosophy at the University of York