Herman Melville, novelist and poet

All visible objects, man, are but as pasteboard masks. But in each event -- in the living act, the undoubted deed -- there, some unknown but still reasoning thing puts forth the mouldings of its features from behind the unreasoning mask. -Herman Melville, novelist and poet (1819-1891)

I wonder if this was written or spoken in connection with Moby Dick, and if it was, what reasoning thing did he intend to be putting forth its features in that great white whale?