In a 'note' at the end of chapter 3 (On the Coming of the Spirit of Truth, John 14:15-24), Don Carson outlines reasons for believing the Holy Spirit is a person (rather than a force or 'thing'). This is more than a theological exercise, since our understanding of the Spirit will affect how we think about God and this will affect our prayers and our worship. I think it is worth sharing in full:
In the exposition of this passage I have assumed that the Holy Spirit is a person, and that traditional trinitarian formulations are both biblical and true. I have not attempted to defend the doctrine of the Trinity (except perhaps implicitly), nor have I attempted to prove that the Holy Spirit is a person. This is because the passage before us does not have such matters as their chief concerns, even though, in my view, it presupposes their essential ingredients.
It may be helpful to list a few reasons why I believe the Scriptures teach the Holy Spirit is both a person and divine. This list is neither exhaustive nor detailed; but it reflects several quite different lines of reasoning which, combined, are convincing.
First, both in this passage and in many others, the Holy Spirit performs personal actions. The Paraclete is a person who comes as Jesus' successor and, in many respects, substitute: a mere influence, or anything less personal and less divine than Jesus Christ himself, would necessarily be something of a disappointment.
Second, the Holy Spirit enjoys both the distinctness and the oneness with the Father that the Son enjoys. The distinctness (e.g. the Father sends the Spirit in response to the Son's intercession) ensures his separate personality; his oneness (e.g. by the Spirit's indwelling in the believer, the Father and the Son also make their home in the believer) ensures his deity.
Third, according to Mattew 12:31-32, a person may sin against the Holy Spirit. Contextually this is more than sinning against the light, or the like. It suggests again (though it does not prove) that the Holy Spirit is a person.
Fourth, the trinitarian formulae in the New Testament are virtually inexplicable if the Holy Spirit, like the Father and the Son, is not both a person and divine. I refer to such expressions as 'baptizing them in the name of the Father and of the Son and of the Holy Spirit' (Matthew 28:19) and 'May the grace of the Lord Jesus Christ, and the love of God and the fellowship of the Holy Spirit be with you all' (2 Corinthians 13:14). To construe the Spirit as less than person and less than divine when the texts put him in the company of deity and speak of his name would be as foolish as to say, 'I baptize you in the name of the Father, and of the Son, and of lovely influences.' The thought approaches blasphemy.
Fifth, although the Holy Spirit is sent from the Father, such 'sentness' does not reduce the counsellor to the status of a thing. After all, John's Gospel makes much of the fact that Jesus himself was sent (e.g. 3:17); and the Gospels do not think of Jesus as impersonal. More to the point, the new testament writers regularly distinguish between the Holy Spirit and his gifts (e.g. 1 Corinthians 12:7-11). Concerning these gifts, Paul writes. 'All these are the work of one and the same Spirit, and he gives them to each man, just as he determines' (1 Corinthians 12:11).
Sixth, older theologians sometimes point to embodiments of the Holy Spirit. At Jesus' baptism, for instance, 'the Holy Spirit descended on him in bodily form like a dove' (Luke 3:22). It is possible, I suppose, to think of God sending a dove to represent a divine blessing or influence or the like; but the language suggests something more: the Holy Spirit descended in bodily form like a dove. It is difficult to predicate such a thing of an influence. The most natural way to take the passage is to think of the Holy Spirit as a person who normally has no bodily form.
Seventh, there are many isolated passages which do not easily fit into one of the previous categories, but which make the best sense if we presuppose both that the Holy Spirit is a person and that the Holy Spirit is God. One example must suffice. In Acts 5:3-4, Peter asks Ananias, 'Ananias, how is it that Satan has so filled your heart that you have lied to the Holy Spirit . . .? You have not lied to men but to God.' The parrallel is obvious.
from Jesus and His Friends (Leicester: IVP / Grand Rapids: Baker, 1980), p64-66
I love the way that Don gives his reasons from scripture. While the broader theological debates are valuable, our theology always needs to be grounded and controlled by the Biblical text.