The understanding of the nature of faith is predicated on understanding theology as a real science begins with the Creator and His revelation. The scientific definition of faith includes all Aristotelean four causes. Faith includes the formal cause—habit, material cause—of mind, when eternal life begins in us—final cause, and making our understanding assent to things not evident—efficient cause.
Faith is a virtue, and it is necessary. It exists in its subject and it is in two powers of the soul: intellect and will. The starting point of the cause helps to understand how the act of our will as a response to grace toward God’s will in love—as St. Paul reminds us in Galatians 5:6—different from some of these commonly held misunderstandings on what is faith—for example, merely blind confidence. Theology depends on faith and revelation, which is how one assents to the propositions of theology as a science—science in the proper sense of all knowledge. In the proper sense of understanding theology as a science—dependent on faith and revelation—one could not be a theologian if one lacked faith because of theology’s dependence of both faith and revelation, one would either be a historian or a philosopher. The primary principle to understand within Catholicism is that faith is our response to revelation, which is grace; a free gift that is an invitation to the Divine life.
The Nature of Faith in the Catholic tradition is likely very different from the common use of the word in everyday usage in the 21st-century secular modernity. For modernity, faith is the blind assent to a proposition; however, this is not the proper sense of the definition of the term within Catholic understanding. Furthermore, the protestant, who is still religious, the meaning of the word is merely to state that one has confidence in Christ and His redemption. In the Catholic understanding, the act of belief as a form of knowledge is distinct from the act of science and the act of opinion. These differences can be distinguished by the Aristotelean model of the three acts of the mind: simple apprehension, judgment, and reasoning.
There are two ways in which a person can come to judgment within this model. The first is philosophical in which one reasons through composing, combining, comparing, contrasting different beings. The second way is the movement of the intellect by an act of the will. Fr. Brian Mullady further explains, “a person may be determined by the will to choose to assent to side…because of something which is enough to move the will, but not enough to definitively move the understanding. For example, one does not know the quiddity of the things through lack of experience but trusts an authority to have such experience or understanding. St. Peter: ‘Lord, I believe, help my unbelief.’”
Jesus, as the one who reveals, gives us provocation to trust in His divinity through the signs of miracles; however, we must be open to such signs and miracles through by the preambles of faith such as God exists. Dei Verbum explains that Jesus Christ is the Prime Revelation and the Prime Revealer. If we’re open to such revelation by the preambles of faith, a person can believe in His divinity because a person trusts in the authority in which Jesus speaks. An example of assenting to the authority and divinity of Jesus through signs would be St. Thomas the Apostle’s response to the sign of touching the man Jesus’ wounds which causes him to assent to the faith of the divinity of Jesus with the response, “My Lord, and my God.”
There are similarities and differences between science and faith. Theology and Science are similar because they both have propositions and certainty. In science, the mind is convinced by the examination of knowledge gained through the senses. After such discourse through examination, assent puts an end to any further dialogue and ends examination. However, in faith, discourse and assent are in movement together at the same time. It is faith seeking understanding “supported by trust in the person revealing, God. Faith exists in the material cause, which is not only God, but “the preambles of faith like God’s existence are necessary” to assent to revelation.
A person, within the Aristotelean model of understanding, may enter into what is called “doubt.” It differentiates from faith because it cannot determine two competing propositions from being true, perhaps, due to a preconceived notion or that the motives of credibility may not be enough to convince. A person may also merely hold an “opinion,” which is different than faith when they accept one proposition, but fear or doubt that other propositions could be true.
The traditional Catholic understanding of the term faith is yet different from that understanding for as the protestant uses the term as a noun, “I have faith,” The intellect may have assented to some propositions of the faith through reason (and not faith) such as historical evidence for Jesus, the use of reason through metaphysics that God exists, or acceptance of signs such miracles by an act of the intellect.
The act of the will is a twofold movement; it is a person’s response to the grace given to us by God through revelation to order our will to His own. When our will assents to faith in Christ, it orders our will to acts of charity as the fruits of that faith. Fr. Brian Mullady explains, “The Church’s teaching is that grace involves the presence of the Holy Spirit dwelling in the soul and accomplishing a true change in the heart of a Christian.”
The Catholic understanding of the nature of faith is more closely related to a verb because it moves twofold from the intellect to faith by revelation and acts of charity. The act of faith is when the intellect is moved by the will assents to the articles of faith given to us by God through revelation. It differs from doubt, opinion, and science because it assents by trust in the revelation of the revealer. It is done by ordering our will with God’s will through acts of charity. As Holy Scripture reveals through St. James, “Faith without works is dead.”
 Fr. Brian Mullady, “Faith (II).” Lecture, Holy Apostles College and Seminary, Cromwell, Connecticut, 2020.
 St. Thomas Aquinas, Summa Theologiae, II-II 4.
 Fr. Brian Mullady, “Faith (I),” Lecture, Holy Apostles College and Seminary, Cromwell, Connecticut, 2020.