What does it mean to “deny the faith”? Fundamentally, it is to walk away from following the Lord Jesus. To deny the faith is to reject him. There are two basic ways anybody might deny the faith and reject Jesus.

Denials of belief

The most obvious way we can deny the faith and reject Jesus is to deny core teaching about who he is and why he came. A denial of belief is essentially a rejection of Jesus in his person – either as fully man or fully God – or a rejection of core gospel truth. Namely, rejecting who Jesus is: saviour and Lord. Rejecting belief in his cross-work and resurrection would be a denial of who Jesus really is. In the same way as with the mouth we profess belief in Christ, so with the mouth we may proclaim that we reject him by affirming beliefs that no longer tally with the gospel.

Denials of behaviour

The other way we can deny the faith and reject Jesus is by the way we live. We might assert belief in Jesus as Lord God and saviour. We may affirm the doctrines of justification by grace alone through faith alone in Christ alone. We may believe that Jesus death was sufficient to pay for sin and that by belief in him and his work on our behalf we will be saved. All the essential doctrine of the gospel may be affirmed by us.

However, we may by our lifestyle – despite the profession out of our mouths – deny the faith and reject Jesus. We may profess to believe but then so live and act as though we don’t really believe at all. We may affirm all the right doctrine but then live ethically, morally and actually as though we don’t believe the things we say nor any of their implications.

Assessing who belongs

When we think about who belongs to Jesus, these are the two basic factors we are looking at. What do they believe? How do they behave?

If somebody denies basic Christian doctrine, they deny by their words that they truly follow Jesus. If somebody denies basic Christian ethics, they deny by their behaviour (or their affirmation of other’s behaviour) that Jesus is truly their Lord and that they are his disciples who aim at obedience of him.

What we are looking for when determining genuine belief in Jesus is somebody who both affirms the basic truths of the gospel and whose life does not appear to undercut their profession of faith. We are looking for a claim that Jesus is Lord and appropriately matching behaviour that behoves someone who follows Jesus. That is to say, somebody who affirms Jesus as Lord and then lives their life in such a way that their claim to follow him appears credible in reality.