Naturally, he was a Jesuit.
He had two main objectives. The first was to come up with a simple, effective model of consciousness that could be used by any discipline. A fair number of people feel that he pulled it off - every years there are conferences where scholars present research based upon the Lonergan model for subjects as varied as sociology and genetics.
His second goal was to demonstrate that the very nature of consciousness draws Man toward God; that our very nature is evidence of the existence of God. Here's a (very) quick rundown of the basics of Lonergan:
There are 4 phases to human understanding;
1) Experiencing: we experience the world (touch a stone, smell a fragrance, etc.)
2) Thinking: we think about our experiences (this stone has protrusions)
3) Judging: we develop an opinion, or we judge something (this stone is rougher than the last stone I felt)
4) Deciding: we determine a course of action, et. al, based upon our judgement (I like smooth rocks more than rough rocks, so I will walk over there).
This is very simplified, naturally, but a good outline. How, you may ask, does this draw Man outside himself, let alone point toward God? Well, each phase of consciousness listed here makes an assumption. In experiencing, we assume that there is, indeed, an objective world to experience. Thinking assumes an objective (and, hence, eventually ultimate) truth; judging assumes the existence of value; and deciding implies an ultimate morality. And all of these things further imply a source, an ultimate from which objectivity springs.
This is closely related to St. Thomas Aquinas' "Prime Mover" concept. and this is purposeful, since Lonergan is a Thomist, or a theologian who bases his work on Thomas Aquinas. Since Lonergan begins with the human being and attempts to demonstrate how humans reach beyond themselves he is often called a Transcendental Thomist