The danger which teachers have to watch is the transformation of the staged performance into a personal argument which can severely damage relationships within the class and so impede learning. Debates, therefore have to be carefully planned and introduced only when the class has already reached a good degree of friendliness and informality. In most classes the principal speakers—preferably two for the proposition and two against—may be drawn from the students, in which case it is desirable for the teacher to be the impartial chairman. The choice of proposition and of speakers, whether students or from outside, should be made well in advance and made known to the whole class. The same points also apply to the so-called panel discussion or brains trust in which a small group with a chairman consider a series of questions. The differences between a debate and a panel discussion are that in the latter a number of issues are considered instead of one propositions, that the tone is more informal and conversational without set speeches, and that a vote is not usually required, whereas in a debate there is a set order of speeches—proposer, oppose, seconder to the proposer, seconder to the oppose, and, in conclusion the oppose followed by the proposer—in the panel discussion the more varied the order the better. Audience participation may be encouraged in either activity; in a debate after the first four speeches and in a panel discussion at any point when it seems likely to take place without a radical distortion of the process. Sometimes most of the class would prefer to listen to the answer given by the panel rather than listen to one or two of their number conducting a personal quiz. Some good use has been made of a divided session, in the first half of which a panel of outsiders answers written questions sent in advance by class members and then proceeds in the second half to ask questions of the class.