[quote="Brendan, post:13, topic:305619"]
To be Catholic requires you to believe that the Church cannot err in it's teachings on matters of Faith and Morals.
When one becomes, or is, Catholic, one accepts that as part of the Faith.
It can be sinful, or it can be actions out of ignorance. If you recognize that you do not understand the Church's teachings and seek to conform yourself, even if not immediately, to the teachings, there is no sin.
If one, out of stubborness and pride, holds yourself to be more knowledgeable than the Church on matters of Morals, and hold, with deliberate thought, that the Church is in error on such matters, then yes, it is sinful.
The infallibilty of the Church on matters of Faith and Morals is de fide, so rejection of such teachings is grave matter. The mortality of the sin therefore depends on how much one freely accepts rejecting the teachings and the fullness of knowledge that rejection of the Moral teachings of the Church are wrong.
[quote="Brendan, post:14, topic:305619"]
This might give you some insights into the matter.
It is from Cardinal Raymond Burke, who is the Prefect of the Roman Rota, kind of like the Church's equivent of the Chief Justice of the Supreme Court.
I'm sorry, but you're mistaken. One does not sin by believing or not believing. One sins by acting or not acting. Intent is only relevant as it relates to an action or omission.
]Dropping a nuclear bomb on an Afghan city to wipe out a Taliban stronghold: **sinful*. Assuming full knowledge and full consent (and given that killing innocent people in the city is obviously grave matter), it's a mortal sin.
]Privately thinking that dropping a nuclear bomb on an Afghan city to wipe out a Taliban stronghold would be a good idea: **not sinful*. It's just a thought or opinion. It is not a sin.
Read through the document you posted from Cardinal Burke. It's fairly clear in discussing sin. It doesn't condemn those who harbor private disagreements with Church teaching.
Check out what Scripture has to say on the subject:
And one of the multitude, answering, said: Master, I have brought my son to thee, having a dumb spirit. Who, wheresoever he taketh him, dasheth him, and he foameth, and gnasheth with the teeth, and pineth away; and I spoke to thy disciples to cast him out, and they could not. Who answering them, said: O incredulous generation, how long shall I be with you? how long shall I suffer you? bring him unto me. And they brought him. And when he had seen him, immediately the spirit troubled him; and being thrown down upon the ground, he rolled about foaming. And he asked his father: How long time is it since this hath happened unto him? But he said: From his infancy:
And oftentimes hath he cast him into the fire and into waters to destroy him. But if thou canst do any thing, help us, having compassion on us. And Jesus saith to him: If thou canst believe, all things are possible to him that believeth. And immediately the father of the boy crying out, with tears said: I do believe, Lord: help my unbelief. And when Jesus saw the multitude running together, he threatened the unclean spirit, saying to him: Deaf and dumb spirit, I command thee, go out of him; and enter not any more into him. And crying out, and greatly tearing him, he went out of him, and he became as dead, so that many said: He is dead. But Jesus taking him by the hand, lifted him up; and he arose.
Jesus said all things are possible if you believe. The father's response made clear that he did not believe everything (else he wouldn't need help with his unbelief); yet Jesus healed his son anyway.
A Catholic who stays with the Church despite an inner inability to agree with some of the Church's teaching is saying "I do believe, Lord: help my unbelief." That's good enough for Jesus; it should be good enough for us.