 These special obligations come in different varieties. Most medieval treatments of the branch of logic are divided by discussions of different varieties. The most common is called ‘positio’, or ‘laying down’. In ‘positio’ a false proposition is laid down at the beginning of the disputation, and the respondent remains obligated to grant it whenever the opponent puts it forward. Modern attention has been mainly on positio. (On ‘sit verum’, see Spade 1994–97 and Uckelman 2015.)