Catholic Doctrine of Conscience
The first principle of ethics is that we should do good and avoid evil.
The great problem of ethics is determining what is good and evil in particular circumstances.
Although it is, in fact, part of the Catholic tradition that conscience is supreme, such that even a poorly-formed conscience ought to be obeyed, this small part of the tradition ought not to overshadow the Church's teaching that it is an obligation of conscience to form our consciences by using objective standards drawn from natural law and the supernatural truths revealed to us by God through the Church.
"Ignorance of the law is no excuse." We are responsible--held accountable by God--for the proper formation of our consciences. It is a great sin against the light to choose ignorance and cultivate sin.
Scripture
"This day I set before you life and death. Choose life!"
Catechism
Misinterpretations of Vatican II
References