literature. It would therefore be impossible to enumerate all the collections; this section presents a survey of the chief representatives of each century and country. Characteristics These rulings are different from those of the previous periods in the nature of the problems presented, in the method of treatment, and in the arrangement of subject-matter. Since the Acharonim saw themselves as no longer having the independence of the Rishonim, they sought to base their decisions on the older authorities. The field had already been thoroughly worked, and the respondent was consequently obliged to make a careful search for the question asked or one analogous to it, in order to provide an answer. Previously, the questions had covered many departments of knowledge, both sacred and profane, being concerned with ethical and philosophical problems as well as with halakhic and exegetic themes, so that there was scarcely a subject of human activity or thought on which the responsa might not expound. Among the Achronim, however, the responsa were restricted almost entirely to legal regulations. Since the pronouncement of judgment was regarded as a religious duty, and since in most countries the Jews were unwilling to submit to a non-Jewish court, legal questions formed a large part of the responsa. Previously, systematic sequence was almost entirely lacking. The responsa of the Achronim had as models the "Arba'ah Turim" of Jacob ben Asher and, after the sixteenth century, the Shulkhan Arukh of Joseph Caro, so that many of the responsa were arranged according to these two works, while among the later scholars this practice became the rule. Earlier responsa had been so lucid that the reader could easily follow them. Among the Achronim this changed completely, for pilpul, which had been in vogue since the mid-fifteenth century in Talmud study, forced its way into responsa literature as well. The responsa are remarkable for the hair-splitting dialectics that characterizes them, and often robs them of lucidity. Fifteenth century The most important German respondents of the fifteenth century were Israel Isserlein and Israel Bruna. The collection of the responsa of Israel Isserlein, "Terumat ha-Deshen", comprises 354 decisions, which are important as describing many characteristic features of the time. Several of them (Nos. 341-346) discuss the apportionment of the taxes and the assessments, while others are concerned with the attitude to be observed toward a repentant apostate (No. 198). Particularly interesting is the responsum (No. 197) devoted to