The so-called great heresies are worthy of examination for a number of reasons, one of which is that they represent the main lines of attack against Biblical Christianity. With the exception of Gnosticism, which begins with the claim to secret knowledge apart from the Bible, they depend on a distortion of the Biblical witness. Modalism distorts the Biblical teaching on the Trinity by making the distinctions mere names and nothing more, masks that one person wears in different roles, giving priority to the texts that speak of the divine unity, but ignoring or downplaying those texts that speak of the reality of the divine persons. Working from a rationalistic basis, it said that Jesus was in some way the same person as the Father.
Like Modalism, Arianism is based on a faulty and partial reading of the Biblical texts through rationalistic presuppositions. While claiming to be Biblically-based, Arianism, like Modalism, smuggles in something other than the Bible to interpret the Bible. The Arian claims to be practising Sola Scriptura, but is in fact doing nothing of the sort.
When we approach the Bible, if we are to be fair, we must approach the Bible as it is and not as we would like it to be. The Bible is not a systematic theology treatise, in which the various doctrines are set out clearly and in order in succession to one another, but is intended to be read and re-read, comparing Scripture with Scripture, thinking things through, and tracing the connections, aided by the Spirit. Attention must be paid to such important matters as historical context (who wrote it, when, and to whom?) and genre (is it poetry, history, or letter?). Attempts to flatten out these things do not end well, because some external principle is always brought in then to arbitrate between “contradictions” created by the false framework of interpretation.