I'd like to pass on an interesting bit of trivia from Father Daniel Brandenburg, who tends to be a treasury of wisdom and information...

Recently a question arose concerning the origin of the “Encounter with Christ” within Regnum Christi. A Belgian priest in the first part of the 1900s seems to have been the first to use the methodology “look, judge, act” and then Pope John XXIII incorporated this into the social doctrine of the Church in his encyclical “Mater et Magistra”. Many groups have used this approach and it forms part of the patrimony of the Church. The 1961 encyclical came out just a few years before Regnum Christi itself was founded, and so had a direct impact on the formulation of the “Encounter with Christ”. We certainly have tweaked and adapted the format of this activity into its current shape (cf. RC Member Handbook #404-425).