Another of Rizal's interests was philology. In 1892, Blumentritt encouraged Rizal to write a Tagalog grammar: "... I am going to suggest to you that during your exile you devote your time to the preparation of a Tagalog grammar. You promised it to me when you were in free Europe but your other pursuits did not permit you to fulfill that promise. There is no one in the Philippines with your talents, your knowledge. Moreover, you are a son of the Tagalog nation, so that no one better than you can provide your people and the whole Malayan world with a grammar of the Tagalog language." Rizal finished this project in 1893, and began in 1894, a Tagalog dictionary on the insistence of European scholars.
Rizal wrote the first psychological essay by a Filipino, La Curacion de los Hechizados (Cure of the Bewitched). He mentioned the paper to Blumentritt in November 1895: "Recently they asked me from Manila to write something about Filipino quacks. I have written an article on witchcraft in the Philippines. I am planning to enlarge it and write an extensive book of superstitions, the mysterious, and the like which in the Philippines are still believed in."