Everyone has a duty to seek out the truth, and it is especially incumbent on the Christian to learn about God and the things of God, so that he may know, love, and serve him all the more. But clearly not everyone is called to be a theologian.
For one thing, not everyone has the time or the intellectual gifts; but more to the point, “sacred theology,” as in the science studied over lifetimes by theologians and taught in seminaries over a period of years, is the special domain of the clergy and of professional theologians. The clergy need to have an expertise in the science of God so that they can guide the faithful correctly; and theologians assist the Church in clarifying, organizing, and delivering this information.
Given the above, to what extent should the rank-and-file faithful attempt theology? We make theological assertions all the time–“God would never do that”; “The angels are like this”–“The universe could have been this way”, etc. But if we lack the schooling to offer any support for our assertions, other than “It makes sense to me,” or “so-and-so said this,” should we refrain from making such assertions? Should we qualify them with “In my lay opinion”? Should we all go to seminary?
A related question would be: where does apologetics end and theology begin, or vice versa?