One can generalize Derrida’s comment on Heidegger as follows: anyone who says something like ‘I must repudiate the entire language of my culture’ is making a statement in the language she repudiates. She will be doing so even if she rephrases her repudiation in the form of a metaphorical, rather than a literal, use of the terms of that language. Alternatively: someone who wants not to talk about beings is compelled to spell out his intentions in — what else? — terms used to talk about beings. Any attempt to do anything of the sort which Heidegger wanted to do will trip itself up. So, Derrida concludes, we must try for something very similar to what Heidegger attempted, but also very different.
Derrida thinks of Heidegger’s attempt to express the ineffable as merely the latest and most frantic form of a vain struggle to break out of language by finding words which take their meaning directly from the world, from non-language. This struggle has been going on since the Greeks, but it is doomed because language is, as Saussure says, nothing but differences.