Usulis (Arabic:الاصولية‎) are the majority Twelver Shi'a Muslim group. They differ from their now much smaller rival Akhbari group in favoring the use of ijtihad (i.e., reasoning) in the creation of new rules of fiqh; in assessing hadith to exclude traditions they believe unreliable; and in considering it obligatory to obey a mujtahid when seeking to determine Islamically correct behavior.