[16] In 1758, he earned an A.M. from Harvard,[17] and in 1759 was admitted to the bar.[18] He developed an early habit of writing about events and impressions of men in his diary; this included James Otis Jr.'s 1761 legal argument challenging the legality of British writs of assistance, allowing the British to search a home without notice or reason. Otis's argument inspired Adams to the cause of the American colonies.[19]
A group of Boston businessmen had been appalled at the writs of assistance that the crown had started issuing to clamp down on colonial smuggling. Writs of assistance were not only search warrants without any limits, they also required local sheriffs, and even local citizens, to assist in breaking into colonists' houses or lend whatever assistance customs officials desired.[20][21][22] The outraged businessmen engaged lawyer James Otis Jr. to challenge writs of assistance in court. Otis gave the speech of his life, making references to the Magna Carta, classical allusions, natural law, and the colonists' "rights as Englishmen".[20][23][24][22]
The court ruled against the merchants. However, the case lit the fire that became the American Revolution. 