From Thomas Joseph White’s The Principles of Catholic Theology, Book 2, page 44:

Where ought one to begin when making discernments about ultimate truth, or what ought we to presuppose as we start out? Arguably we should not leap immediately to the question of ultimate reality, but we should start instead with the topic of ordinary reality as we perceive it all the time. What is indisputably real? Interestingly, Christian, Jewish, and Muslim philosophers in the high Middle Ages who were inspired by Aristotle started their philosophical investigations typically not with reflections on God but with reflections on what they called “common being,” the kinds of things we experience all around us, and moved from these to the consideration of God. How then can we think non-controversially about the multiplicity of realities that we typically experience? What properties do they all have in common? To address thes question, medieval philosophers developed the concept of the transcendentals: being, unity, truth, goodness, and beauty. These are basic notions of reality that we inevitably make use of when we think about ordinary reality as we encounter it every day. They emerge in us naturally and inevitably as we begin to think about realities around us, in their natures and properties. Since these notions are very basic, they are something all persons inevitably employ, including those who hold to any of the distinctive worldviews we noted above (and any others for that matter). Such notions stem from considerations in ordinary experience of what exists and does not exist, the multiplicity and unity of beings, their truth and falsehood, their goodness and the reality of evil, and the beauty in things and their potential ugliness. Everyone inevitably thinks about these things, no matter how basic their reflections may be. Transcendental notions are so general that everyone makes use of them in some way, even if they never reflect on this usage self-consciously. We should consider each of them briefly, then, as it concerns our investigations. Why? If we can identify a general form of metaphysical realism that is natural to all human beings in virtue of their intellectual activity, we can in turn identify the foundations in reality from which these notions derive. Subsequently we can consider how those foundations (structures of being themselves) provide an indication to us of what is ultimately real. This will allow us progressively to think in a constructive and focused way about the controverted question of the truth of Christianity.