Clark takes issue with the traditional threefold-view of faith (fides) on the grounds that adding "trust" (fiducia) to the threefold understanding of faith (fides) is tautological. That is, Reformed Christians have traditionally understood faith as a combination of knowledge (notitia), assent (assensus) and trust (fiducia). For Clark, however, "fides" (faith) means the same thing as "fiducia" (trust).
The crux of the difficulty with the popular analysis of faith into notitia (understanding), assensus (assent), and fiducia (trust), is that fiducia comes from the same root as fides (faith). Hence this popular analysis reduces to the obviously absurd definition that faith consists of understanding, assent, and faith. Something better than this tautology must be found(Clark).
Clark focuses on Thomas Manton's exposition of this view, which he articulates in his commentary on James:
Quoting James 2:19 about the devils, Manton remarks that the faith here is a “bare speculation” and cannot possibly save anyone. That this faith cannot save is very true. It is no more than a belief in monotheism. This the Moslems possess. But, however it may be with Moslems, it seems incorrect to call the faith of devils a bare “speculation.” This word often is used to refer to some proposition that is so unverifiable as to be more likely false than true. Granted, Manton also calls it a knowledge; and this is better, because on this point, if on nothing else, the devils believe the truth.
He continues: “Thou believest; that is, assentest to this truth.” Belief therefore is an act of assent to the truth. Yet Manton adds, believing is the “lowest act of faith.” In view of all the Scriptural commands to believe, this sounds very strange. Is there then a higher act of faith? And if so, is it higher because it has a more detailed object-i.e. a greater number of propositions-or because the elements of the act of believing are different?
Manton continues with the object of this belief: “There is one God. He instanceth in this proposition, though he doth limit the matter only to this.” This is a now rare usage of the verb, not noun, to instance. It means, to give an instance; the proposition, “there is one God,” is therefore an instance or specification of what the man believes. Manton suggests that the man believes or assents to “other articles of religion.” This is doubtless true, for nearly everyone who believes in any sort of God believes something else about him beyond bare existence. That the man has an extensive Jewish or Christian theology, however, is not clear because the devils are soon said to believe the same propositions.
Manton, Clark notes, suggests that adds "consent" to assent and knowledge. The devils are not "resting" in their knowledge of God. Whatever the merits or lack thereof with respect to Manton's distinctions, I don't think Clark deals with the passage very closely. There are two problems:
1) According to James, the problem with the demons is not that they do not assent to enough propositions. The problem is that they are not obedient to God. They therefore give evidence, like James' congregation, that they are not elect. Let's look at the text:
14 What good is it, my brothers, if someone says he has faith but does not have works? Can that faith save him? 15 If a brother or sister is poorly clothed and lacking in daily food, 16 and one of you says to them, “Go in peace, be warmed and filled,” without giving them the things needed for the body, what good[a] is that? 17 So also faith by itself, if it does not have works, is dead.
18 But someone will say, “You have faith and I have works.” Show me your faith apart from your works, and I will show you my faith by my works. 19 You believe that God is one; you do well. Even the demons believe—and shudder! 20 Do you want to be shown, you foolish person, that faith apart from works is useless? 21 Was not Abraham our father justified by works when he offered up his son Isaac on the altar? 22 You see that faith was active along with his works, and faith was completed by his works; 23 and the Scripture was fulfilled that says, “Abraham believed God, and it was counted to him as righteousness”—and he was called a friend of God. 24 You see that a person is justified by works and not by faith alone. 25 And in the same way was not also Rahab the prostitute justified by works when she received the messengers and sent them out by another way? 26 For as the body apart from the spirit is dead, so also faith apart from works is dead(Jas. 2:14-26)
James does not say: "You believe that God is one; you do well. Even the demons believe - and shudder! Do you want to be shown, you foolish person, that this alone makes you no different from a Muslim or an "Orthodox" Jew?" Indeed, v. 18 makes it clear that the rest of the literary unit, ending in v. 26, is about how a merely notional faith is inadequate because it does not produce obedience. Obedience is not instrumental to our salvation, of course, but it is evidential of our salvation.
19 For what can be known about God is plain to them, because God has shown it to them. 20 For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world,[g] in the things that have been made. So they are without excuse. 21 For although they knew God, they did not honor him as God or give thanks to him, but they became futile in their thinking, and their foolish hearts were darkened(Rom. 1:19-21).
Unbelievers know God. When we preach Christ, they suppress the truth in unrighteousness (Rom. 1:19-21; Acts 7:51). What is knowledge? It is justified true belief. Therefore, even "unbelievers", by virtue of their possession of knowledge, possess some sort of belief. Indeed, the Jews are described as having possessed some sort of notional faith that was nonetheless non-salvific:
"23 Now when he was in Jerusalem at the Passover Feast, many believed in his name when they saw the signs that he was doing. 24 But Jesus on his part did not entrust himself to them, because he knew all people 25 and needed no one to bear witness about man, for he himself knew what was in man"(Jhn. 2:23-25).
These same Jews apostasize from Christ (Jhn. 6, 8). That is precisely why Christ did not trust them (Jhn. 2:23-25, 6:64). This 'faith' is mere assent and knowledge, although it lacks trust.
2) The demons clearly do not merely assent to the proposition that there is one God. This is rather more likely, as Manton points out, one example of many important propositions to which one must assent. The demons are also well aware of the fact that Jesus is the Son of God(Mk. 1:24, Matt. 4:1-11, 8:29, Lk. 4:34). Manton, as Clark points out, cites passages where the overwhelming emphasis does admittedly seem to be assent to the proposition that Jesus Christ is the Son of God(1 John 4:2 and 5:1; 1 Corinthians 12:3; Matthew 16:17). Indeed, Clark seems to approve of the supposed position of the Reformers: "This is what Manton refers to as “the mistake of the former age.” Thomas Manton was a Puritan of the seventeenth century, and when he speaks of “the former age,” he is not referring to apostate Romanism, but to the Reformers themselves. Hence he is a witness that they defined fait has an assent to the promise of the Gospel"(Clark).
Clark, Gordon. "Saving Faith." The Trinity Foundation, 1979.