Truth is all around us. It is something concrete and is not able to be changed. For one to come to truth one must have a knowledge of that truth. In this case there is natural and supernatural knowledge. Man is a creature of reason, and it is through this reason that man differentiates himself from lower creature. However, there are limitations to natural knowledge, and to understand divine truths, or supernatural knowledge, the grace of God must be present.
For one to know any element of truth, God must first move the intellect to do so . Supernatural grace is not something needed to know natural knowledge. This can be seen in many places in sacred scripture, but probably most famously in Romans chapter one. One of the verses in question is Romans 1:20 which states, “Ever since the creation of the world his eternal power and divine nature, invisible though they are, have been understood and seen through the things he has made. So they are without excuse” (NRSV). Natural knowledge, great as it may be, is limited in scope. Through natural knowledge we can know that God exists, and we can come to a know the end of things, scientific processes, and we are to relate to each other.
Grace changed things and allows us to obtain supernatural knowledge. This does not mean that we will be understand all things about the divine, but God touches us and raises us up. We become fully dependent on God and God works through us. This supernatural knowledge brought about by grace gives a a reinforcement “to the power of the soul over the body, of reason over the passions, of man over the world, belongs to the sphere of preternatural gifts, which we might call miraculous” (Journet 5.5). Furthermore, this supernatural knowledge of knowing that we are fully dependent on God and understanding that we cannot do anything apart from him, helps us persevere in grace and charity (Hardon Ch. 3).
Hardon, John. History and Theology of Grace. Ann Arbor, MI: Sapientia Press, 2005.
Journet, Charles. The Meaning of Grace. Princeton: Scepter Publishers, 1997.