Pope S. Callistus: "He chose us"

In love he destined us for adoption to himself through Jesus Christ,
in accord with the favor of his will

-- Eph 1:1-10

"O blessed light, O Trinity and first Unity!" God is eternal blessedness, undying life, unfading light. God is love: Father, Son and Holy Spirit. God freely wills to communicate the glory of his blessed life. Such is the "plan of his loving kindness", conceived by the Father before the foundation of the world, in his beloved Son: "He destined us in love to be his sons" and "to be conformed to the image of his Son", through "the spirit of sonship". This plan is a "grace [which] was given to us in Christ Jesus before the ages began", stemming immediately from Trinitarian love. It unfolds in the work of creation, the whole history of salvation after the fall, and the missions of the Son and the Spirit, which are continued in the mission of the Church.

-- CCC 257