By this we know that we abide in him and he in us, because he has given us of his Spirit. And we have seen and do testify that the Father has sent his Son as the Savior of the world. God abides in those who confess that Jesus is the Son of God, and they abide in God. So we have known and believe the love that God has for us (1 John 4:13-16).There are an interesting number of parallelisms present in these brief verses, and they can prove illuminating for understanding John's own theology of the Spirit.
On the one hand, the mutual abiding of God and the Christian is known through the possession of the Holy Spirit. Yet this possession cannot be separated from confession: those who confess that Jesus is the Son of God abide in God, and God abides in them, too. John perhaps make this clear in light of the dangerous teachers afflicting his target audience, who might even have claimed to have the Spirit of God but who denied that Jesus was the Son of God. He certainly has false teachers in mind when writing this letter, for he mentions them: I write these things to you concerning those who would deceive you (2:26). Over and against these false teachers, John consistently appeals to his authority as a member of the apostolic community (cf. the eyewitness claims in 1:1-4). So this provides a fine measure of a person's possession of the Spirit of God: does that person confess that Jesus is the Son of God, or not? If he does not, then that person cannot have the Spirit -- whatever other manifestations of spirituality there might be.
On the other hand, there is also a close connection between possession of the Spirit and certain conceptions about God's attitude towards us in Jesus Christ. Notice how John defines the apostolic confession: we have seen and do testify that the Father has sent his Son as the Savior of the world. Of course, if Christ is the Savior of the world, then he is my savior too! A person who possesses the Spirit of God will not live in servile fear of God, worrying constantly about being stricken or damned with no trust in God whatsoever. On the contrary, the Spirit of God convinces us of the love that God has for us, as John says. This is echoed also in Paul's theology of the Spirit: For you did not receive a spirit of slavery to fall back into fear, but you have received a spirit of adoption. When we cry, "Abba! Father!" it is that very Spirit bearing witness with our spirit that we are children of God (Rom 8:15-16). The Spirit convinces us that God is fundamentally for us; that his primary attitude towards us is one of love and concern, and that he has made us his children.
So we see, then, that possession of the Spirit, for John anyway, is closely connected to a Christian's beliefs and confession. The Spirit convinces us that God is love (1 John 4:8) and makes us aware of that love as it has been manifested and expressed through Christ (vv. 9-10). In this way, we can see how the Holy Spirit to some extent directs our attention to Christ as the unique medium through which the love of God and his salvific concern are made known. It is hard not to draw the inference that, as far as John is concerned, the Holy Spirit will not draw our attention to some other would-be savior, since certainly these were available at the time of his writing. On the contrary, the Holy Trinity brings us to itself and not to another: the Spirit opens our eyes to Christ, and Christ reveals to us the love of the Father.
I hesitate to make another point here, as well. If a part of the confession of the Spirit is that Jesus is the Savior of the world, what sense can we make of theologies which attempt to limit the salvific intent of God in Christ to something less than the whole world? It seems clear to me that "world" in this context means "all human persons," because this is evidently the way that John uses the phrase when previously talking about the atonement of Christ: He is the atoning sacrifices for our sins , and not for our sins only but also for the sins of the whole world (2:2). Because he is atoning for the sins of the whole world, consequently the "whole world" has to be understood as human persons, who have sins to be atoned, rather than some other impersonal object. Yet if this is the way that John is using the word "world," then can we draw the conclusion that predestinarian theologies which limit the salvific intent of God in Christ are not from the Spirit?
If John is dealing with gnostic teachers afflicting his congregations, then it might not be a stretch to think that a part of their false teaching included a kind of predestinarian anthropology: some spiritual types are destined to gain saving knowledge of secret truths, whereas other, more earthy types are destined never to go beyond the awareness of the body and its passions. This kind of ontological predestination would have been unsatisfying to John, as I am reading him -- not because of the kind of determinism involved, but because it limited the salvific scope of God's work in Christ. This doesn't mean that John was a universalist; it means, however, that as far as God is concerned, John understands him to desire and to work for the salvation of all, though this might not be accomplished because of human freedom.
Whether or not I ought to push this latter point about predestination, I don't know. Certainly it doesn't follow from this that Calvinists and other predestinarians don't have the Spirit; my own experiences contradict such an extremist conclusion. But I am not very sympathetic to Calvinist predestinarian theology, though I can see the various arguments in its favor. In any case, the greater point of my posting is this: the Spirit, according to John, convinces us of the love which God has for us in Jesus Christ, and leads us to confess this.