In the Gospel today, Mark tells us twice that Jesus, even at the start of his ministry, "taught with authority." He didn't cite experts, or base himself on what others before him had taught: it was "a completely new teaching, in a spirit of authority." And that authority extended even to the powers of hell, as the people in Capernaum witnessed when Jesus cast the tormentor from an possessed man.
The whole question of teaching is the question of authority. So many people today reject what the Church teaches simply because, not acknowledging the Church's authority to teach (especially when it comes to matters that people would rather decide for themselves), they do not even "hear" the teaching. The Theology of the Body is perhaps the biggest example of this. Statistics indicate that close to 90% of self-identified Catholics reject the Church's teachings in the area of marriage and sexuality. (At that rate, one should first inquire how many self-identified Catholics even know, with some degree of accuracy, just what those teachings are. But I digress.) But when people are presented with the Theology of Body, many of them are astonished. This is "a completely new teaching" and, yes, it is given "in a spirit of authority." What makes the difference? Perhaps the secret lies in the way the message comes to them. Not in condensed version through the news media or pop culture, not in a vague reference in a homily, but in the same way that the Gospel itself was originally, and effectively, communicated: from neighbor to neighbor, sharing good news.