Often (and it was the case here) the singularity of such works is due principally to their having been executed in special conditions for which we do not at first sight make proper allowance, if, for instance, the strange attire of a feminine model is her costume for a masked ball, or conversely the scarlet cloak which an elderly man looks as though he had put on to humour some whim in the painter is his gown as a professor or alderman or his cardinal's cassock.