For generations Baptists have asked, "what does it mean to be a Baptist?" Exploring the life of Thomas Patient is helpful in finding an answer to this question. An English Puritan, then an American Baptist, then an English Particular Baptist, Patient's life of faithfulness and dedication to sound doctrine culminates in his foundational role in establishing the Baptist movement in Ireland. Although unknown by most Baptist historians, this exploration of the convictions and theology of Patient's life and ministry illustrates this under-appreciated figure's role in locating the Baptist identity. Through exploring Patient's extensive and early treatment of the doctrine of believer's baptism, Caswell grounds Baptist identity not fundamentally in the doctrine of soul competency, but rather in the biblical doctrine of believer's baptism. The life and ministry of Thomas Patient reminds readers why Baptists have been called Baptists. The Baptist identity is one distinguished by its unwavering conviction to the biblical doctrine of believer's baptism by immersion.