Mental Illness and the Case of Phlogiston

I recently came across this 2001 article by Thomas Szasz arguing that mental illness is for psychiatry what phlogiston was for chemistry. The much derided and marvellously named phlogiston was a hypothesized substance, supposed to exist within flammable objects and make it possible for them to burn. As a theory it was initially quite useful, but came under pressure when it failed to accurately predict that burnt metals increased rather than decreased in weight. Ultimately phlogiston theory was supplanted in the 1770s when Lavoisier discovered Oxygen, helping to lay the ground for modern chemistry.

Phlogiston is often cited as a neat example of a defunct scientific theory, and Szasz seems to be using the idea to deride psychiatry for retaining the idea of mental illness; phlogiston is an analogy for anachronism. Mental Illness was always, for Szasz, an idea in urgent need of retirement.

However, the lessons phlogiston theory offers psychiatry are more complicated than Szasz allows.

Hindsight is a wonderful thing but, as Kuhn points out in The Structure of Scientific Revolutions, phlogiston theory had plenty of predictive power and much value for understanding the world in the late 17th and early 18th centuries. Still now it presents a philosophical puzzle. Phlogiston turned out not to exist, but the early chemists who spoke about it were on to something. Did the term describe, to some extent, the nature of the world? After all, it turned out that something had existed all along (Oxygen), but no-one had possessed the conceptual apparatus to describe it.

Talk of Kuhn is apt in this connection, for the field of mental health has seen recent calls for a “paradigm shift” in relation to how it conceptualises its objects of study. This call has met resistance, some of it organized around the feeling that diagnoses, and the concept of mental illness still have some value in mental health care. Perhaps mental illness isn’t the same as physical illness (it certainly attracts more animus), but there are ways in which illness as a heuristic plays a role in recognizing the ways that people can be overwhelmed psychically by psychosis, mania and swingeing depressions.

Nonetheless, if you subscribe to Kuhn’s vision of how inquiry proceeds, a paradigm shift is always essential for the successful development of science, and certainly we are presently confronted with a host of conceptual difficulties when discussing mental illness. Just look at this article by the psychologists who run the DOTW blog, and then this response by Guardian blogger Dean Burnett. Read both of them and see if you too get a sense that both perspectives have something important which should not be lost; the ambivalence you're feeling is a sure sign of the conceptual uncertainty under which we currently labour.

Unfortunately paradigms are not just things to be shifted, they are ideas that give order to programmes of research, allowing the accumulation of useful knowledge. They do not get chased out of academic discourse by activists, but wither up and die on the vine when something better comes along. Phlogiston-theory suggests that it takes a superior replacement ideas, not just criticism, to put paid to inaccurate concepts.

Thomas Szasz was more right than he knew.