It strikes me as distinctly odd - one could say perverse even - of Hugh Willmott (Letters, February 23) to defend Foucault and Derrida as champions of "radical enlightenment" and to lump them in with Habermas, who rightly calls their forms of relativism and holism reactionary and self-defeating.
Foucault's reductive materialism, collapsing mind and the ideal into the material, and his antihumanist demolition of subjectivity, mean no difference - and hence no dialectics - between positive and negative terms: freedom and constraint, concept and object, agency and structure.
This also applies to Derrida's linguistic determinism and indeterminacy of meaning reducing the world to signifier and text, his deconstruction without reconstruction.
It can be said that Habermas too does not have the criteria (of perception) to show whether we are great minds thinking alike or small ones who seldom differ.
But when modish, influential theories are themselves presented as "invisible dogmas" and not as claimed, then we have to ask what hope there is for the unexamined life snapping its chains?