Presbyterian minister, later practiced medicine, Member of Colonial Assembly, Member of Council of Safety, 1775. Commanded First Delaware Militia Regiment. This regiment, reviewed in Dover, later joined Washington's army and fought in Battles of Long Island and White Plains. It disbanded December, 1776. Haslet continuing with Washington's army was killed Battle of Princeton, January 3, 1777. Buried First Presbyterian Churchyard, Philadelphia. Re-interred here 1841, when address was delivered by John M. Clayton.