Imagine someone saying that they love Jesus, but they abhor sacred doctrine and theology. As unfortunate as this sounds, it is something that happens on a daily basis within Christendom. There are also those, some through no fault of their own, that do not understand the importance of sacred doctrine. Understanding of sacred doctrine is important in many facets of our lives, not just the spiritual.
Sacred doctrine is important because we are oriented toward God, and this orientation exceeds that which we can describe. These truths are given to us by divine revelation. Some of these may have become known by some, but over time error would creep in (ST 1, Q1, A1). Sacred doctrine is important because it is taught by divine revelation. Furthermore, it is important because it is the study of our creator, and if we truly love him, we would strive to know everything possible to build a stronger relationship.
Sacred doctrine and the use of reason are not at odds. Quite the contrary, reason can lead to some truths of sacred doctrine (ST I, Q1, A1). However, reason can only get us so far and we eventually need to be enlightened by God to other truths. Sacred doctrine includes the philosophical and natural sciences. This is because both have their origins in God, and sacred doctrine is the study of God. As St Thomas Aquinas states, “But in sacred science, all things are treated of under the aspect of God: either because they are God Himself or because they refer to God as their beginning and end” (STI, Q1, A7).
Thomas Aquinas. Summa Theologica. Trans. Fathers of the English Dominican Province. London: Burns Oates & Washbourne. Print.