We have recently concluded the book of 1 John in church, and the Bible Study I attend should finish it this week, Lord willing.
1 John is an interesting book for a lot of reasons. It contains probably the simplest Greek of any New Testament book, evincing none of the polish of Dr Luke or Paul, but rather uses short and simple phrases. The book describes a number of tensions, usually resolved by treating the participles in chapter three as we treat the English progressive tense.
It is generally interpreted, I think, as a response to libertine Gnostic influence in the church, especially due to repeated emphasis that Christ came in the flesh. As a rule, I am generally wary of hermeneutics that rely overmuch on historical positioning, since I think they lend themselves to abuse,
1 but in this case I am somewhat more supportive. First, because 1 John, despite its grammar and vocabulary, is a difficult book. Second, because it helps to unify things nicely.
There were evidently a wide variety of Gnostic groups, but they generally shared a common soteriology (salvation by knowledge) and, as I see it, a denial of physical reality. The flesh is seen either as evil of itself, or as a cosmic mistake of sorts, and so the idea of the humanity of Christ was, to a Gnostic, reprehensible. To the Christian, of course, Christ is
more human than his followers.
The libertine Gnostics (there were plenty who were ascetic) evidently felt that due to the flesh's inferiority, fleshly actions were inconsequential—somehow less real than the spiritual. So it was acceptable, for example, to live licentiously because the spiritual world was untouched by the physical.
The Gnostics found in Christianity the
logos that they desired; Christ was sent to enlighten and reveal divine knowledge. The notions of enlightenment and reason (whence, I suppose, comes knowledge) are pertinent especially because the Gnostics used similar terms with dramatically different meanings.
John begins the letter very explicitly arguing for the physical nature of the incarnation. The gospels, especially Luke and John, record that he appears physically after his resurrection. He was tangible—the wounds remained, and the disciples could probe them. He ate food, and made careful effort to demonstrate he was not a phantasm or spirit, but a flesh-and-blood human being.
He carries the theme of the incarnation throughout. We see it interspersed often with the strong moral overtones of the book: the repeated emphasis from John is that we are to love one another. At the outset, we see that the book concerns fellowship, both with God (through, e.g., confession), and with each other (through, e.g., love).
It is important to see the anti-gnostic perspective in the verse, "If we walk in the light, as he is in the light, ... his blood cleanses us from all sin" (1Jn 1.7). We err, I think, if we suppose that "walking in the light" means "not sinning"; if we didn't sin, then we would not need cleansing. To the sort of gnostic John preached against, one who was enlightened knew that there was no sin—naturally the sort of reaction we would get in this case is, "But I don't sin!" or "Sin is made up!" But 1.8 follows, which plants us firmly in the reality that sin exists.
The topic of love is not disconnected from this. If we forsake the reality of sin, we lose our understanding of love. Why? Because Christ was manifested to take away our sin. Our understanding of love is depends on how we perceive his sacrifice, and since the gnostics disclaimed the reality of the flesh and thereby the reality of sin, they could not love. We see it distorted into lust by the libertines and condemned by the ascetics. One of the most powerful revelations of God's love for us is given in 1Co 13.
I think we may also find here an oblique statement about the spiritual corporeality present in Christianity. We perceive, and rightly, the corruption of our flesh, both material (we start to die the moment we're born) and spiritual (it is bound by sin). But we are not allowed to believe that this is the purpose and end of the flesh; rather, we are told that we will be raised in incorruption (1Co 15).
This is, I think, why Christ is called the firstfruits. As he was raised, so shall we: in bodies that do not decay. We shall be like him, in that we have no sinful nature. We'll finally be free.
The Gnostics, I think, treated the flesh as inherently corrupted. This leads us in two different paths, both expressed in Gnosticism: licentiousness and aceticism—lives of wantonness and deprivation. This is not what we look forward to.
[1] In particular, I worry that we may be inclined to treat the Scriptures as time-bound when implementing an historical hermeneutic. Some are inclined to look at the moral commands of Scripture as culturally irrelevant, as evidenced by a number of groups that wish to remove bans on homosexuality or to ordain women. Not surprisingly, I find that those who are loose in their theology also tend to be loose in their morality (in the sense that they have a much-reduced perspective of sin; I am not saying that people with loose theology perforce live licentiously).