How is the test given in 1 John 4:2 any good, when in Mark 5:6–7 the demoniac called Jesus the Son of the Most High God?

This text is from a transcript of a talk by David Gooding, entitled ‘Unity, Origin and Victory’ (1987).

Here is a man inhabited by a legion of evil spirits. In spite of that, when they protest, he, or they, or both, acknowledge Jesus as the Son of the Most High God. Therefore the question asks, how is the test given us in 1 John 4:2 any good? If evil spirits are prepared to acknowledge that Jesus is the Son of the Most High God, then they would come through the test with flying colours. But that isn't quite true, is it? We are dealing with evil spirits and we must be aware that we're dealing with something exceedingly sophisticated. You will notice that 1 John 4:2 doesn't say 'every spirit that confesses that Jesus is Son of the Most High God is of God', does it? What you're required to confess is that he is the Christ come in flesh. You see, many spirits and many false systems like theosophy, if you ask them about the Lord Jesus, will say, 'Of course he's the Son of God.' Then they'd add, 'We're all sons of God anyway, and God being the most high, yes Jesus is the Son of God most high. Everybody's the son of God most high anyway.'

What they wouldn't confess, if you pressed them, is that Jesus is the Christ, because though they do believe he is in some sense, not in our sense, but in their sense, the Son of God, they hold that the Christ is the great world Spirit and they will not admit that Jesus is the Christ. They'll twist all the ways round they know how. They'll say that the Christ used Jesus or Jesus was filled with the Christ. They will not admit that Jesus is the Christ and I take it that John is being exceedingly exact when he lays down this test.

Comment on Matthew 7:21–23

I think here we must take our Lord very, very seriously. We've been thinking in our studies through the epistle of John of the tests that are given us as to whether our profession of faith is genuine. Now we are to notice that in those tests John doesn't say, 'Look, if you have prophesised, or if you have cast out a demon, you are a child of God.' It's possible to prophesy and cast out demons and not to be a child of God. Our Lord warns us about it, so that we must be very careful to listen to these tests that our Lord himself gives us. It's not because he's narrow minded or something like that. In that day, if people should come and say, 'We cast out demons in your name. We prophesied in your name' our Lord will say, 'Sorry, but that is not the test as to whether a person is a child of God or not.' I don't want to be rude, but Balaam's donkey prophesied at one stage, didn't he? It's not necessarily a test that somebody is a child of God.