In Against Heresies, Irenaeus spends the first two books understanding the Gnostics and refuting them at every turn. His arguments are logical, but more importantly they are biblical. In contradistinction from Justin Martyr and Origen, who baptize philosophy with Christian truth and nomenclature, Irenaeus is a biblical apologist in the purest sense. The Gnostic Christians have misinterpreted the Bible, misconstrued the doctrines of the faith, and misled the Church by conjoining the pure Word of God with the perverted philosophies of Greek mythology. In Against Heresies, Irenaeus responds by highlighting the disparity between their false arguments and the plain reading of Scripture. He does this in three ways.
First, Irenaeus contends with the Gnostics because they derive their principles of doctrine from the irreligious philosophers of the day. Instead of appealing to the Bible they imitate Thales, Anaximander, Plato, and the Pythagoreans. The only difference is the nomenclature. Irenaeus writes, “These men (the heretics), adopting this fable as their own, have ranged their opinions round it, and if by a sort of natural process, changing only the names of the things referred to, and setting forth the very same beginning of the generation of all things, and their production.”
Second, Irenaeus lists numerous ways in which the Gnostics strain the gnat and swallow the camel. They import meaning into letters, syllables, and numbers, while disregarding the composite testimony of the biblical writers. Likewise, they parse out meaning in parables that do not relate to the singular meaning of the Lord’s instruction.
Third, Irenaeus charges the Gnostics with an atomistic reading of Scripture that fails to recognize authorial intent, biblical context, or the unified formation of Scripture. In this, Irenaeus distinguishes the use of biblical language and biblical truth. Concerning this vain imitation, he says, “by these words [the Gnostics] entrap the more simple, and entice them, imitating our phraseology.” The Gnostics deceitfully appropriate the former to deny the latter. He says,
They gather their views from other sources than the Scriptures; and, to use a common proverb, they strive to weave ropes of sand, while they endeavor to adapt with an air of prophets, and the words of the apostles, in order that their scheme may not seem altogether without support.
Continuing his rejection of the Gnostic system of interpretation, Irenaeus says, “the method which these men employ to deceive themselves, while they abuse the Scriptures by endeavoring to support their own system out of it.” Rather than reading the Bible in context and searching for an inductive meaning in the text, these false teachers were conscripting words, ideas, and atomistic elements of the text to support their preconceived systems of thought. Irenaeus continues, “collecting a set of expressions and names scattered here and there [in Scripture], they twist, them, as we have already said, from a natural to a non-natural sense.”
The problem with this is that it superimposes on the Bible the ideas and theological constructs of the reader. The intention of the author and message of the Spirit is distorted and lost. Though centuries before postmodern, reader-oriented hermeneutics, this is essentially what Irenaeus is refuting. He is contending against any kind of allegory which says “this means that,” what you see in this passage actually means that person, that Aeon, that god, or that idea drawn from the system of the reader. Irenaeus’ conclusion articulates well how contextual readings undo this allegorical nonsense.
If he takes [the verses lifted out of context] and restores each of them to its proper position, he at once destroys the narrative in question. In like manner he also who retains unchangeable in his heart the rule of the truth which he received by means of baptism, will doubtless recognize the names, the expressions, and the parables taken from the Scriptures, but will by no means acknowledge the blasphemous use which these men make of them. For, though he will acknowledge the gems, he will certainly not receive the fox instead of the likeness of the king. But when he has restored every one of the expressions quoted to its proper position, and has fitted it to the body of the truth, he will lay bare, and prove to be without any foundation, the figment of these heretics.
 Cleveland Coxe summarizes these books, “The first of these contains a minute description of the tenets of the various heretical sects, with occasional brief remarks in illustration of their absurdity, and in confirmation of the truth to which they were opposed. In his second book, Irenaeus proceeds to a more complete demolition of those heresies which he has already explained, and argues at great length against them, on grounds principally of reason” in The Anti-Nicene Fathers (Peabody, MA: Hendrickson, 1994), 311. Irenaeus employs logic, but his polemics are biblically-informed and rich with illustrations and explanations from the Bible.
 Ibid., 2.16.1. In this statement, Irenaeus is referring to the account of an unrecongnized “cosmic poet” by the name of Antiphanes, whose cosmogony started with Night and Silence which begot Chaos, then Love from Chaos and Night, and then finally Light.
 Ibid., 3.15.1. He reiterates this point, “Such men are to outward appearance sheep; for they appear to be like us, by what they say in public, repeating the same words as we do; but inwardly they are wolves” (Irenaeus Adversus haereses 3.16.8).
 Ibid., 1.8.1.
 Ibid., 2.9.4.