Catalonia's dovish regional business and knowledge minister, Santi Vila, announced on Twitter on Thursday night that he had resigned.

"My attempts at dialogue have failed once more", said Mr. Vila: "I hope to have been useful to First Minister Carles Puigdemont and to Catalans up until the last minute".

On Tuesday, Health Minister Dolors Montserrat said Mr. Vila "and possibly some other regional ministers" would likely resign if attitudes within the Catalan government shifted towards an attempt at a unilateral breakaway from Spain.

On October 5, Vila wrote an article in pro-separat...