A person claiming to be Catholic but holds things that are alien to the faith, when they manifest their heresy in public, by that fact alone, they are outside the Catholic Church; without any formal declaration.
Yes. This is true. I’m really pleased that someone has made this remark. There is a distinction between automatic and formal excommunication:
Automatic is immediate without need of approval from authority within the Church and which can be relieved by means of confession; this obviously entails their sorrow to God that they did or said whatever it was which brought about that effect upon their soul.
Formal has to be exacted but also relieved by ecclesiastical authority and normally to do with an explicitly phrased public denial of some aspect to the Catholic faith. Appropriated as a rule to those denounced as heretics.
To note, the word ‘heretic’ is a word that is fine in usage but was and still is talked down by those in indirect defence of apostacy (although it has to be said that their words often expose that they have become imposters).
Saints over the centuries have built up the Church. They filled hearts with words driven by God. While imposters will drag you down in effect as they carry out desecration.
‘Matthew 18:6’
‘Whomever takes one of these little ones of my arms, it would be better they had a millstone around their necks’.
The terrible effects of heresy are beyond reckoning and shouldn’t be overlooked. Christians are God’s children. There is much heresy about and so make sure you know your own faith. If you have a problem understanding some element, instead of being a heretic go immediately to God and pray with reference to ‘Mark 9:24’:
‘(God)…I do believe, help my unbelief’. And continue to pray it, until you do understand.
This is a well-known prayer within the Church. Pity more people don’t pray it, instead of spouting falsity.