I first read this book as an undergrad economist, well over 10 years ago now. I discovered the book, in the course of writing about the evolution of the Phillips curve. What the Phillips curve offered, initially at least, was the embodiment of empirically-based economic theory, yet it metamorphosed, into the New Classical 'expectations-augmented' model, and the New Business School model with each, in turn, becoming accepted 'truth' by mainstream economics. What could account for this shift? Clearly it was not based on anything related to 'positive' economics or empiricism, since the theory behind the 'curve' (which was no longer a curve)had long since been wrung dry of any meaningful empirical content.
While I don't recall all of the details, this book, and McCloskey's other writings on the same theme, support the idea that, while Truth (to be differentiated from trivialities, things that are true 'by definition', for example), does exist, WE HAVE NO WAY OF COMING TO RECOGNISE IT - there are no objective criteria for doing so, that is distinguishing truth from falsity. It may come as a shock to some, but there is no dissenting from this point - if you know of any such criteria, let me know.
The slightly controversial, but logical, point that follows is, therefore, to disregard Truth as a 'useful' concept, with any explanatory power. The key to the acceptance of theory (as if it were the Truth), not just in economics, lies ultimately in its 'persuasiveness', something that is engendered through the use of 'mere rhetoric'. McCloskey is not arguing that this is how things 'should' be, but how they are - in grubby, messy reality.
If you doubt this to be so, try thinking about the recent Gulf War and arguments about WMD, as an illustration - it was Bush and Blair's ability to 'persuade' people, and politicians, that made the threat from Iraq real, or 'True'. That is, the threat might have existed independent of their pronouncements, but because we had no objective means of evaluating that, their pronouncements BECAME REALITY.
This is a text about the philosophy of economics that is extremely thought-provoking. It succeeds in challenging preconceptions of what is True and how we come to know it as such, that has implications far beyond economics. For anyone with an interest in philosophy, or economics, this is well worth reading, a real eye-opener.
Lord Chimp, the relativists will inherit the world, my friend. Like it or not, there is no black or white, only shades of grey, and neither is counterintuity synonymous with absurdity.