Cheshire Cat could not leave its grin behind it" enlightened us "about the nature of things". For what we learn from these principles is of considerably greater and more general practical importance. Thus, for example, the conclusion that "it is not the consciousness of men that determines their being, but their social being that determines their consciousness", or, more generally, that "being is prior to thinking", is at once more generalised than a principle about cats and their grins, and what we learn from it is in practice more important for ussince in practice no one gets led astray by supposing that grins exist independently of faces, whereas many get led astray by supposing that thinking or consciousness exists independently of real individuals and their social being. Similarly with conclusions about the dependence of qualitative changes on quantitative ones, and other "laws of dialectics".
If we consider principles of materialist dialectics, such as those mentioned as having been first formulated by Marx and Engels, my contention in this chapter is that they evidently differ from the generalisations arrived at by the empirical sciences in that they are not established and tested by the same type of directed observation and empirical test, and that their applicability in the guidance of practice is therefore also not of the same sort. Their character and application is essentially that of "laws of thought", as Engels already emphasised when he included "dialectics" along with "formal logic" in "the science of thought and its laws", stressing that it was demonstrable "independently" of "the positive science of nature and history".
However, this does not entail, as Kant supposed in his fanciful theory of "synthetic a priori knowledge", that they are somehow spun out of the inner resources of the mind and imposed by the mind upon "the phenomenal world" which it constructs for itself as its "object". On the contrary, they are indubitably and universally true of the processes of the real world, which we get to know about, but which proceed in accordance with these "laws" independently of our knowing them. Such a contention can appear paradoxical only to those who are still under the spell of the old antitheses of a priori and a posteriori, or of "analytic" versus "synthetic" knowledge.
The distinguishing feature of principles of materialism and dialectics is that they concern categories. They lay down correct ways of assembling relatively abstract items of information in order to arrive at concrete and informative conclusions. Category principles, considered in their aspect as reflecting objective reality or "the nature of things", are characterised by their absolute generality (corresponding to Aristotle's conception of truths true of "being as being"), in distinction from generalisations of natural or social sciences which deal with particular classes of phenomena. As I have said, this "quantitative difference" of degree of generality marks a "qualitative difference" in the character of the generalisations.
Of course, as Engels often and justifiably insisted, such generalisations, far from being spun out of the mind from its own inner resources independent of all experience (the conception of the mind spinning anything out of itself independent of experience is absurd) are arrived at as a result of experience. And naturally, errors or crudities in their formulation may be detected as a result of contradictions with experience. But the test or demonstration of the correctness or otherwise of such generalisations goes beyond merely ascertaining their empirical confirmation. Their demonstration depends on demonstrating, not as with empirical laws that they are not in fact falsified, but that to imagine their falsification results in "absurdity" or "fancy" in the sense of uninformativeness.
For example, Marx's principle that "social being determines consciousness" was arrived at by studying the facts of human history, and criticising the conclusions reached by historians and sociologists who proceeded on an opposite pri