Immanuel Kant’s famous distinction between the noumenal and the phenomenal world naturally poses problems for metaphysics. The noumenal world is the intelligible world or the world of things-in-themselves where, if we had access to it, we would be able to understand our sensible experiences in the phenomenal world. Access to the noumenal world would include understanding pure ideas such as justice and courage as well as an understanding of causes and effects seemingly found in our world. But, according to Kant, we do not have access to the noumenal world and are stuck in the phenomenal world, the world of appearances, where we can only make speculations about what is really going on. We cannot make synthetic a priori judgments; in other words, we cannot make any universal truth claims based on our experiences in the world. Our link between experience and truth is cut off. In light of this, Kant must reject metaphysics since we are unable to make any metaphysical claims about reality. Metaphysics may exist but we have no way of knowing anything contained in it.
However, Kant appears to take a step closer to the noumenal world in his third critique, Critique of Judgment. In this Critique, he discusses how aesthetic judgment links art to morality. As Wood puts it, “Our shipwreck in the theoretical order points to the real purpose of our faculties: moral action in this world”  Art brings out our act of judging and through this act which reflects both freedom and nature, Kant may be finding a unity between the world of appearances and the world of truth. Wood argues, “The whole region of reflective judgment – the beautiful, the sublime, and the organic – points to the possibility of the insertion of causality through concepts into the mechanical world of nature and thus serves to bring together the fractured halves of the field of thought . . .” 
Though Kant would not claim that human judgment is a starting point for metaphysics, others, such as Bernard Lonergan, do offer such a proposition. Lonergan seeks to understand the human faculty of judging (along with the other human faculties) in order to first, find a method for how we come to know things (epistemology) and second, to discover a starting point for metaphysics. In his carefully structured 700 page masterpiece, Insight, he slowly finds that the capacity to judge or “revise” the world is where we can find truth about the sensible world. In the Chapter 14, “Method of Metaphysics,” he states, “Bluntly, the starting point of metaphysics is people as they are.” 
Sadly, Kant was unwilling to make such a claim, although perhaps he was drawing closer to it in his third critique. Lonergan, in contrast, offers this rather simple starting point for metaphysics: people as they are. People have the unusual capacity to judge the world around them, have insights, revise insights and slowly build up a dynamic set of metaphysical principles. Though all other metaphysical principles are able to be questioned, the fact that we are questioning is unquestionable. Thus, the fact that we are revisers cannot be revised: “for there is no revision of revisers themselves.” It may seem like an obvious principle to grant, but as Lonergan attempts to do, from it, one can begin to discover many other metaphysical principles along the way.
This is not to say that this principle is the only starting point for metaphysics. Certainly, there are many other points on which to begin as philosophers have shown over the centuries. For, if there really is a metaphysics, there will be more than one way to find it.