Justification is a declaration.
When a person is justified by God he declares that they are in the right. He has found in their favour and they have right standing before him. This is the language of the law-court and is therefore sometimes referred to as the forensic, judicial or juristic understanding of justification.
Both Piper and Wright acknowledge the place of the law-court within justification, and they both accuse the other of down-playing this imagery! This does make one full of hope for a resolution to this debate.
This declaration is what we call today a 'speech-act'. Through his declaration, God has created a new status for the person justified. The status that someone has when the court has found in their favour is what is called 'righteousness'. This status implies the forgiveness of sins, since within this setting humanity is seen as being in the dock facing a guilty verdict. Within this law-court setting 'righteousness' has nothing to do with moral righteousness. This is why this view is sometimes seen as a legal-fiction. We will need to go on to examine the language of righteousness, particularly the 'righteousness of God', and to ask what is going on in this declaration. What is the relationship between the 'righteousness of God' and the 'righteousness' which is ours as a status as a result of God's declaration?
Augustine thought that justification was more than just a declaration. He thought that justification involved a transformation as well. We are actually made righteous. This was thought to be through an impartation of some of God's own righteousness into the believer. We shall go on to explore the difference between this and the reformation view of imputation, and how this differs (or not) from what Wright is saying.
Wright is keen to set this law-court imagery within a Jewish setting, and within the framework of the covenant, rather than some later version of a law-court such as in the time of Anslem, or Calvin.
Of course there are many other things involved in someone 'becoming a Christian' including baptism, unity with Christ, reception of the Spirit which enables us to say 'Abba Father' and 'Jesus is Lord', reconciliation, regeneration etc, etc. Part of what Wright is trying to do, is to be specific about what Paul meant by justification in context without using it as a short-cut term for all of these things. Lots more that could be said about declaration of course but that will have to do for now.