differing only in being even more general, then that simply exemplifies confusion in the use of the words "law" and "general" (admittedly very confusing words), since the latter are empirical laws and the former are not. There is not a shred of evidence to suggest that Engels was actually guilty of any such confusionthat he really thought that, for example, the "law of transformation of quantity into quality" was a transformation law of the same logical type as, say, the first law of thermodynamics. Some of his interpreters did afterwards perpetrate such confusionbut Engels himself simply did not deal with such logical questions, which had not yet been raised at the time he was writing. The point can, if one likes, be put like this—that the difference between these laws is not only a quantitative difference, of degree of generality, but a qualitative difference; they are different kinds of law, or exemplify different uses of the word "law".
Perhaps the difference can be most perspicaciously brought out in terms of Dr Popper's criterion for a "scientific" (or empirical) law. Such a law, he said, must be falsifiable. Sure enough, the laws of thermodynamics, for example, are falsifiable, even though never actually falsified. But principles or laws concerning categories, including "the most general" ones, or universal "laws of dialectics", are not falsifiableor if they are, they are not correctly formulated. For instance, certain scientific or empirical laws stating and forecasting how particular changes happen state and forecast how certain quantitative changes bring about certain qualitative ones. Such laws are subject to empirical test (falsifiability), as to whether the connection of qualitative with quantitative change is always in fact as stated. But that qualitative and quantitative changes are always connected is not similarly subject to test. That they are connected in a particular way in a particular case has to be empirically established or disestablishedbut not that they are connected. Thus "the law of the transformation of quantity into quality" is, as Engels said, exemplified in scientific laws, and in that sense it may be said to be "abstracted" from the same factual data as are generalised in scientific laws. But at the same time it is not a more general empirical law, comparable to scientific laws, and the method of arriving at its formulation and of testing its correctness is entirely different.
In his inaugural lecture at Oxford (Philosophical Arguments, 1945) Professor Ryle said that "a pattern of argument which is proper and even proprietary to philosophy is the reductio ad absurdum". He was evidently referring to those arguments in philosophy which concern, in his phraseology, the logical investigation of categories. Correctly formulated principles concerning category, or "category propositions", are such that their breach results in "absurdity"—and this is the test of such principles. That (I believe) is in principle correct. But he had earlier ended his paper for the Aristotelian,, Society on Categories by asking: "But what are the tests of, absurdity?" And this vital question was still not answered. In criticising, above, the linguistic interpretation of category, I suggested the way of answering this question.
The kind of absurdity that results from breach of category principles is not the same thing as violation of the rules of the actual or significant use of given languages. For example, it is no more a violation of those rules to say that quantitative changes can go on and on indefinitely without involving qualitative changes (which Hegel and Marx said should not be said), than it is to assert the independence and immortality of ghosts which temporarily inhabit the machines of our bodies (which Ryle and Marx said should not be said). The "absurdity" of such statements consists rather in what I have called their uninformativeness.
Those very simple and obvious examples of "category mistakes" which linguistic philosophers quote from Lewis Carroll are of this kind. For example, when the White King 