What must a Catholic believe to be a Catholic? What must a Catholic believe to be a Catholic? I know we must believe the articles in the Nicene and Apostolic Creeds and the Ex Cathedra statements about Holy Mary's Immaculate Conception and Assumption. What else must be believed, to be a practicing Catholic, according to the Catholic Church?
Truths absolutely necessary for salvation
The four truths absolutely necessary to believe for salvation are that

&quot;he [God] is&quot;, i.e., that God exists (Heb. 11:6)
God &quot;is a rewarder to them that seek him.&quot; (Heb. 11:6)
the Second Person of the Trinity took on a human nature (Incarnation)
God is Three Divine Persons in one God (Trinity)

Note: There is unanimous consent among Catholic theologians that truths #1 and #2 are absolutely necessary to be explicitly believed in order to be saved, but not all theologians (St. Thomas Aquinas, St. Alphonsus Liguori, et al. excepted) think that explicit belief in truths #3 and #4 is necessary; cf. True or False Pope p. 113 // PDF p. 128.source
Truths necessary to be Catholic
To be Catholic, one must, as the asker writes, indeed &quot;believe the articles in the Nicene and Apostolic Creeds and the Ex Cathedra statements about Holy Mary's Immaculate Conception and Assumption&quot; (cf. the 4 Marian dogmas).