Pilpul (פלפול, loosely meaning 'sharp analysis'; ) is a method of studying the Talmud through intense textual analysis in attempts to either explain conceptual differences between various halakhic rulings or to reconcile any apparent contradictions presented from various readings of different texts. The word pilpul has entered English as a colloquialism used by some to indicate extreme disputation or casuistic hairsplitting. The requirement for close derivation of the conceptual structures underlying various Jewish laws, as a regular part of one's Torah study, is described by Maimonides as follows: A person is obligated to divide his study time in three: one third should be devoted to the Written Law; one third to the Oral Law; and one third to understanding and conceptualizing the ultimate derivation of a concept from its roots, inferring one concept from another and comparing concepts, understanding [the Torah] based on the principles of Torah exegesis, until one appreciates the essence of those principles and how the prohibitions and the other decisions which one received according to the oral tradition can be derived using them.... Other such sources include Pirkei Avot, the Babylonian Talmud, Rashi, and Shneur Zalman of Liadi. In the narrower sense, pilpul refers to a method of conceptual extrapolation from texts in efforts to reconcile various texts or to explain fundamental differences of approach between various earlier authorities, which became popular in the late fifteenth and early sixteenth centuries: its founders are generally considered to be Jacob Pollak and Shalom Shachna. Pilpul was defined by Heinrich Graetz as "the astonishing facility of ingenious disquisition on the basis of the Talmud." Many leading rabbinic authorities have harshly criticized this method as being unreliable and a waste of time, and it is regarded by some as having been discredited by the time of the Vilna Gaon.