The concept vita apostolica embraced three basic principles: imitation of the primitive church, poor, simple, and penitential, with interests and activities restricted to the spiritual domain; a passionate love for souls at home and far afield; and evangelical poverty in common, either predicated on mendicancy or mitigated by the work of one's own hands. It became, during the age of Gregorian reform and after, a compelling program instinct with the fervor, spontaneity, and humanity of the first community at Jerusalem (Acts, iv, 32; cf. Luke, x, 1–12). It postulated reform and criticism in a restless age of expanding economic and geographical horizons, a more rational political system, an increasingly complex social organization, a multiplicity of divergent intellectual currents, and corresponding new spiritual needs. Such a momentous evolution of society, challenging the status quo in all its parts, demanded a reappraisal of the resources and ends of the church, the most powerful and tenacious defender of tradition.