I insist that in general there are two categories of truth: subjective or objective. Subjective truth is not necessarily true universally such as when someone insists that for them it is true that God exists: “I believe that God exists.” On the other hand, objective truth is something that is universally true regardless of personal belief, e.g. “God exists.” There are different methods to validate the veracity of these truths, but modernity has seemingly eliminated all other methods as hokum, opting instead for a purely scientific methodological approach. The scientific method to validating truth is useful but cannot be said as the sole method. In other words, to insist that things are only true if they are scientifically verifiable is absurd.
There are two reasons that make the demand for all truths to be subjected to scientific investigations absurd. The first arises from the competence of the discipline of science and its object of study. Scientific data are those which are observable in the physical universe (observational access may require some use of technological apparatus) in some controlled environment. However, there are things that science cannot study, viz. things that are immaterial. Consider for one moment the concept of God. According to our understanding, God, by definition, is perfect, immutable, and therefore must be immaterial since to be material is to be subjected to potency—to potentially to become more or less perfect—and therefore God cannot exist in a physical form. Because God does not exist in a physical form, it cannot be demanded that He subjects Himself to empirical verification since the demand for a non-empirical entity to subject itself to empirical verification is a self-contradictory demand. The belief that something exists outside a system cannot be disproved by observing the behavior of that system. Just as a fish would not be able to disprove its human owner’s existence by observing the waves and lighting of the tank, humans cannot disprove of God’s existence simply because we cannot observe him with even our most powerful and complex apparatus.
The second reason arises from a logical inconsistency in the demand itself. The demand that all truths be verified by scientific investigations holds in itself an implied truth, namely that the only truths that can be said to be true are those which science has verified as such. In other words, the demand holds that any truth must be scientifically verifiable. Yet, the truth of the demand—that all things are true if they are scientifically provable—is not scientifically provable. This is to say that the physical sciences cannot prove that the only acceptable truths are those that have undergone scientific investigations. Such a truth, if it exists at all, is a priori and is presupposed. Yet, such an a priori truth belongs mainly and essentially to the philosophical discipline and not the scientific discipline.
Since truth is beyond empirical verification, it is therefore abstract and categorical in being. Truth is categorical in this sense insofar as it can be labeled as ontological or logical, i.e. that which exists extramentally or only in the mind. Yet, these truths are nevertheless alike in some sense because they have some sort of “being.” Being-as-such is being considered in its totality and in general—it is being qua being. When the mind grasps a thing or concept—either that which has actual existence or that which has existence only in the mind—being is grasped as both limited and unlimited. It is grasped as limited in the thing or concept which the mind conceives and apprehends, but being is grasped also as unlimited as the horizon against which the limited being is placed in contrast (this is a Rahnerian concept understood by his supernatural existential). Such apprehension of the truth of being can only be approached with a science which moves beyond mere empirical considerations and mere rational considerations. Therefore, this apprehension must come from a science which considers that very first act of a thing, i.e. its existence, in order to place it in context of the totality of the real. Such a science is called the science of metaphysics, and, if we are to have a clear understanding of the unlimited horizon of being against which limited being is in contrast, we need to know what being is and the modes in which being is known. We need, therefore, to turn to metaphysics for help in apprehending the nature and intelligibility of being.
In short, our Catholic faith does not reject the invaluable aid that the sciences provide in coming to know truths, but it does realize that the sciences is one among the many methods of doing so.
 Ontological truths encompass empirical truths including those which the scientific discipline provides, but it does not limit itself to simply that since ontological truths move beyond the empirical to the immaterial, e.g. the human soul, angels, and God.