conception later in his life, closer to evolution. In any case the above argument is an anti-realist one, in the diremption that it introduces between thought and reality. The answer to this is not to say that reality obeys some 'laws of the mind' or something, but rather to say that mind obeys the laws of reality (i.e. nature, material world, etc.),of which it is, quite naturally, a part. Mind is not somehow outside of reality. As a general rule one might say that if material
[WS:] It is anti-realist in the sense that realism presupposes the real existence of the so-called universals (http://en.wikipedia.org/wiki/Universal_(metaphysics), http://en.wikipedia.org/wiki/Problem_of_universals) or general (abstract) concepts. The realist position is that they exist in the real world independently of human cognition, human mind merely discovers them.
My position is closer to that of Kant - our perception of reality is directed and determined by apriori categories of mind (http://en.wikipedia.org/wiki/Kantianism) they are not fully "subjective" i.e. arbitrary (they are socially determined as Durkheim aptly argued) yet they do not exist in reality , but rather they are forms of organizing perceptual material. Some of those forms are better than others in that task, and what makes them better or worse is contradictions - the more contradictions, the poorer the fit between an a priori form and reality.
With that in mind, the way I interpret Marxian "contradictions" is that it was a critique of the bourgeois political economy that legitimated a particular institutional order rather than a critique of that institutional order itself. That is to say, the argument is that bourgeois political economy does a half-assed job justifying the institutional order of manufacturing and distributing goods that developed in the 18th/19th century aka "industrialism" or "capitalism," because the same assumptions that underlay the bourgeois political economy can lead to the opposite conclusions, i.e. that the institutional order in question is not the best of all possible world, but rather it may collapse under its own weight. AFAICT, Francis Wheen adopted a similar interpretation in his biography of Marx.
This is an epistemological position, not an ontological one. It means that the bourgeois conceptual apparatus to describe (and legitimate) industrial or "capitalist" relations is shaky, rather than the institutional order itself is shaky. If the latter can indeed be viewed as "shaky" it is not because of some logical properties of it (i.e. "contradictions") but because there are social forces out (the proletariat) there that have both the reason and the capacity to challenge and perhaps overthrow that order.
Wojtek