e 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 misunderstood Alice's statement that she "saw nobody on the road" he was expressing the curious view that the person Nobody is the person who is there when no visible or tangible person is there. This raises a laugh; but its "absurdity" is of the same kind as that perpetrated by primitive peoples and theologians who say that your immortal soul is that part of you which thinks and feels and acts when you yourself have ceased to think or feel or act. Of the same order of absurdity is the statement that the Cheshire Cat's grin remained after the Cat had disappeared. Some such absurdities are very easy to recognise, and are funny; and others are not so easy to recognise, and are serious. To the latter class belong those absurdities which result from breach of the general principles of materialism and dialectics. The point of these general principles, and what makes their formulation worthy of being called "the science of thought and its laws", and their observance as essential for right thinking as is observance of the laws of formal logic, is that they are the principles for maintaining informativeness and removing illusion and fantasy.
We can very well speak, if we want to, in violation of laws of dialectics, of things which are not affected by other things and are eternal, indestructible and changeless. Language permits us so to speak, and it involves no grammatical or syntactical error, no violation of principles of formal logic and no logical contradiction. But if we try to describe a world consisting of such things, then we are describing something unrecognisable and unverifiable. For how could we recognise anything or verify its existence unless it affected us in some way? And how can anything which is fixed and changeless and does not interact with anything else possibly so affect us? To speak of such things is to speak of things in principle unverifiablelike, for example, Leibniz's monads. Statements about them are uninformative or, as Engels put it, "fantastic", or as Ryle puts it, “absurd".
Similarly with 