Complex sentence: Christopher Smart (1722--1771), an English poet, was confined to mental asylums from May 1757 until January 1763; many who knew him believed that he suffered from madness during the mid- 1750s.
Split into simpler sentences: Christopher Smart (1722--1771), an English poet, was confined to mental asylums from May 1757 until January 1763. It was alleged by many who knew him that he suffered from madness during the mid- 1750s.