I have been thinking a great deal about an essay by Jacques Derrida titled “White Mythology: Metaphor in the Text of Philosophy”. In this essay, Derrida speaks of a coin so old that the images stamped on its heads and tails have worn away. This coin still has some currency, but its provenance is uncertain and, as a result, its value is considered increasingly suspect by those who give it and take it in turns. Derrida holds that philosophical concepts that do not bear any mark of their cultural provenance or any mark of the facticity of their issuers are similar to such coins: such concepts may have currency but their value is suspect.