These are two different ways of achieving the same thing
Permission is from the classical school
Redecision is from the redecision school
Both of them are designed to alter the injunctions in the life script.
To change the injunctions Eric Berne proposed the permission transaction as shown below
If the client accepts the permission then the injunction is kind of nullified or overpowered by the permission and from that time on the Child ego state of the client listens to the permission instead of the injunction. Therefore they will think, feel and behave in a way that is injunction free (script free).
A redecision is a decision made by the A1 or Little Professor ego state to reject the original injunction given by the parent. This diagram shows how a young child accepts the original injunction from the parent
If the A1 makes the redecision then the original injunction looses all its power and effect in the personality and again the person will begin the think, feel and behave in a way that is injunction and script free.
To make the redecision the Goulding’s employed the gestalt therapy technique of two chair. The original parent figure is in one chair out in front of the client. In the client’s chair is the Child ego state. And at the point of redecision the A1 in the client’s chair decides to reject the original early decision to accept the injunction.
Children will tend to make their early decision to accpet injunctions when they are under stress