Nancy Cartwright knows how to write about philosophy of science. Are fundamental (theoretical) laws true and what is their relation to reality? This is the sort of questions Cartwright deals with.

What is her seminal publication “How the Laws of Physics Lie” (1983) about?

The primary aim of this book is to argue against the facticity of fundamental laws.

Pardon, for example?

The vector addition story is, I admit, a nice one. But it is just a metaphor. We add forces (or the numbers that represent forces) when we do calculations. Nature does not ‘add’ forces. For the ‘component’ forces are not there, in any but a metaphorical sense, to be added; and the laws that say that they are there must also be given a metaphorical reading.

Yes, I agree. It is not necessarily clear that different forces can simply be added (or how they can be added). For example, are deformation forces and gravity force in fluid dynamics ontologically the same?

We may use the fundamental equations of physics to calculate precise quantitative facts about real situations, but as I have urged in earlier essays, abstract fundamental laws are nothing like the complicated, messy laws which describe reality. […]

Ok, I see the point. What is then the “simulacrum account” for (conceptual) models?

The second definition of ‘simulacrum‘ in the Oxford English Dictionary says that a simulacrum is ‘something having merely the form of appearance of a certain thinking, without possessing its substance or proper qualities.’ This is just what I have been urging that models in physics are like.

Ok, so models are not reality either. However, models are closer to reality than fundamental theories?

A model is a work of fiction. Some properties ascribed to objects in the model will be genuine properties of the objects modelled, but others will be merely properties of convenience.

A work of fiction?

Imagine that we want to stage a given historical episode. We are primarily interested in teaching a moral about the motives and behaviour of the participants. But we would also like the drama to be as realistic as possible…

Ok, I understand. Physics as theatre!

Physics is like that. […] Adjustments are made where literal correctness does not matter very much in order to get the correct effects where we want them; and very often, as in the staging example, one distortion is put right by another.

At least, we hope so.

In brief, Cartwright states that the explanatory power of fundamental laws does not argue for their truth. She proposes a simulacrum account of explanation, namely the route from theory to (mathematical) conceptual model and from conceptual model to phenomenological law. She states that fundamental laws are only true with respect to the (mathematical) conceptual model.

Key words of the work are: “unprepared description” (first step of theory entry which is informal) and preparation of the description (with bridge principles), fundamental theories and phenomenological theories

For me, compared to other books on philosophy of science this work ist both, entertaining and illustrating. It provides the broad view and gives many references to other philosophers such as van Fraassen, Hume, Duhem and others. On the other hand it gives very specific and detailed examples of quantum mechanics.

Enjoy reading!