[T]he unknown of a science is not what empiricist ideology thinks: its “residue,” what it leaves out, what it cannot conceive or resolve; but par excellence what it contains that is fragile despite its apparently unquestionable “obviousness,” certain silences in its discourse, certain conceptual omissions and lapses in its rigor, in brief, everything in it that “sounds hollow” to an attentive ear, despite its fullness.