The object of discussion in the science of Fiqh is the act of mukallaf viewed from the side of syara 'law which is fixed for him. A faqih discusses the sale and purchase of mukallaf, rent, pawn, representation, prayer, fasting, pilgrimage, murder, accusations against adultery, theft, pledges, and wakaf done mukallaf, so he understands the law syara 'in all these deeds.
The object of discussion ushul figh science is syar'i proposition that is general in terms of legal preciseness that is general as well. So a ushul scholar discusses about qiyas and his end, about the proposition "Amm and its limits, and of command (amr) and dalalaahnya, and so on.