We will now identify and discuss four principles utilized by the federal theologians.
3. The Analogy of Faith (Analogia Fidei)
Muller defines analogia fidei as follows:
the use of a general sense of the meaning of Scripture, constructed from the clear or unambiguous loci…, as the basis for interpreting unclear or ambiguous texts. As distinct from the more basic analogia Scripturae…, the analogia fidei presupposes a sense of the theological meaning of Scripture.
An example of this would be interpreting texts that speak of the humanity of Christ in the wider textual-theological context of the incarnation of the eternal Son of God. For example, in Acts 20:28, God is said to have purchased the church “with His own blood.” “Be on guard for yourselves and for all the flock, among which the Holy Spirit has made you overseers, to shepherd the church of God which He purchased with His own blood.” From other texts of Scripture, according to the principle of analogia fidei, we learn that Christ, according to his divine nature, is invisible (John 1:1, 18). So, according to the analogy of faith, we can affirm that God has blood, in so far as the person of the Son has blood, according to his human nature.
The inspired and infallible rule of faith is the whole of Scripture whose textual parts must be understood in light of its theological whole. This insures that the theological forest is not lost for the textual trees.
The principle of analogia fidei gained confessional status as follows: “The infallible rule of interpretation of Scripture is the Scripture itself…” (2LCF 1.9).
 Muller, Dictionary, 33. Cf. Walter C. Kaiser, Jr., Toward An Exegetical Theology (1981; reprint, Grand Rapids: Baker Book House, Sixth printing, January 1987), 134ff., where Kaiser fails to distinguish properly between analogia Scripturae and analogia fidei and advocates what he calls “The Analogy of (Antecedent) Scripture.” In the conclusion to his discussion (140), he says, “However, in no case must that later teaching be used exegetically (or in any other way) to unpack the meaning or to enhance the usability of the individual text which is the object of our study,” emphasis Kaiser’s. This is, at worst, a denial of the historic understanding of analogia fidei and, at best, a very unhelpful and dangerous modification of the doctrine. It seems to me that this would mean, for example, that we cannot utilize anything in the Bible outside of Gen. 1-3 to help us interpret it. Since there is nothing in the Bible antecedent to Gen. 1-3, interpreters are left with no subsequent divine use, no subsequent divine explanation of how to understand that passage. This method ends up defeating itself when we consider that Genesis (and all other books of the Bible) was never intended to stand on its own and that the Bible itself comments on antecedent texts, helping its readers understand the divine intention of those texts. Kaiser’s method seems to imply that the exegesis of a given biblical text is to be conducted as if no subsequent biblical texts exist. We must realize that, in one sense, we have an advantage that the biblical writers did not have–we have a completed canon. But we must also realize that the Bible’s use of itself (whenever and wherever this occurs) is infallible. If this is so, then the exegete, using tools outside of the biblical text under consideration, ought to consult all possible tools, which includes how the Bible comments upon itself no matter where or when it does so. If the Holy Spirit is the only infallible interpreter of the Bible, then certainly exegetes ought to utilize biblical texts outside of Genesis to aid in the understanding of Genesis. It seems to me that Kaiser’s proposal would give warrant for exegetes to consult commentaries on Genesis to aid in its interpretation, but deny the use of the Bible itself (which contains inspired and infallible commentary) to that same end.