It is altogether different with knowledges such as philosophy and theology. Philosophy (metaphysics, epistemology, philosophy of nature, moral philosophy…) is capable of emitting irreformable assertions, in other words absolute truths, because it bears on intelligible being itself, or the real attained purely and simply (and not only as to the observable as such). When it says the true, and to the extent that it says the true, that which it says is absolutely true, and true for always. This is that to which the primary and most deep-seated ẻlan of the intelligence tends, and that for which it is most fundamentally thirsty.
When we say that truth is the adequation of the intelligence and of that which is, this is understood therefore primarily and above all of the adequation of the intelligence with “that which is” purely and simply, as it is the case for philosophy and theology. And it is understood secondarily (by extension to a type of knowledge enclosed completely in that which appears to the senses) of the adequation of the intelligence with “that which is” under a certain relation only (under the relation of observability), as it is the case for the sciences of phenomena.
Philosophy, which bears on the intimate intelligible structure of that which is, absolutely speaking, and theology, which bears on the intimate superintelligible mystery of Him Who is, absolutely speaking, are types of knowledge exceptionally difficult in themselves. This is why man has so often erred in them.
In science, knowledge less elevated and more narrow, which is a late fruit of human thought (it began only in the sixteenth century to disengage itself in its proper nature), and which bears on the rational interpretation and the rational organization (above all, there where it is possible, mathematization) of that only which appears to the senses, man errs also but does not cease to correct his errors with an inviolable regularity, because the retracing of the intelligence imposed by such a type of knowledge requires particularly rigorous methods and specializations; but the truth which we have then to do is truth only secundum quid, approximate truth.
The Scientists know this; the noninitiated do not know it. Let us turn, in a last remark, to the side of the human community. If the idea that no higher knowledge, neither philosophy, nor theology, is capable of absolute truth became generally accepted, the result would be that the world of culture would find itself, ─not through the fault of science, ─mystified by science. For it is the assertions of science, haloed with its dazzling application, which a multitude of people who are not scientists would take then for “the truth” (absolute) of which by virtue of the very nature of the intelligence they experience unconsciously the need; whereas the scientists would continue to know, and better and better, that, however precious the progresses of science may be, irreformable assertions and absolute truths are not of the domain of the latter.
~Jacques Maritain: On the Church of Christ, Chap. IV, n. 4.