Here’s a quote that would do a lot of justice to Johnstone’s concept of philosophical controversy. It is taken from the writings of Levi Strauss – more precisely, from one of his many discussions with Stern on the notion of historicism:
“Historicism claims that all human thoughts or beliefs are historical and therefore bound to die; but historicism itself is a human thought; therefore historicism itself has a limited validity, or else it cannot be true. To assert the historicist thesis means to doubt it and, thus, transcend it” (Levi-Strauss, 1953, Natural right and history)
To Johnstone, remember, philosophical controversies are alway recognizable by this trait that one party accuses the other one of not being able in principle to fully assert a thesis. A reasonable attack of inconsistency, as it were, or a “valid ad hominem” – in Johnstone’s terminology. It was responded to - just as predicted (see review link below) – with an accusation of straw man:
[…] let us rather admit that historicism cannot claim timeless validity without violating its very principle. […] By virtue of the categories at our disposal at this moment of history, human thoughts, beliefs and values appear historically conditioned […] Since, besides the categories of our epoch, we have no others at our disposal […] we must say that, in our epoch, historicism appears to be a well established theory. The fact that we cannot affirm the eternal, timeless, transhistorical validity of historicism does not exclude the possibility of its being valid for the present historical epoch which gave birth to it. (Stern, 1962, Philosophy of history and the problem of values)
Now, the question is when is an accusation of fallaciousness – dialectically – reasonable? Can you ever unreasonably accuse someone of being unreasonable?
The debate is treated from the perspective of controversy analysis in
Dascal, M. (2008). Dichotomies and types of debates. In F. H. van Eemeren, & B. Garssen (Eds.), Controversy and confrontation (pp. 27-51). Amsterdam/Philadelphia: John Benjamins.
The edited book will be reviewed here in a couple of weeks.