He received his schooling in Kilkenny, then moved for a short time to Maynooth. From 1808 to 1814 he studied in Dublin, where in the latter year he was ordained to the priesthood. Having entered the Capuchin order, after a brief period of service at Kilkenny, he joined the mission in Cork.
Father Mathew did not believe in gradual approaches or temporary commitments. He advocated a promise that meant complete commitment. It did not bind like the vows of marriage, but the principle of permanent commitment was the same. Fr. Mathew understood that as long as the act of will continued, it could overcome all difficulties.
One simple commitment, encased in the words of the Total Abstinence Pledge, supposedly did the trick. The surroundings did not make much difference. One could take the pledge as a single individual or as one of a waiting line coming up in a parish, mobilized and brimming with enthusiasm for the occasion. However, Father Mathew arrived at this conclusion only after much prayer for guidance and after urging by others who proposed total abstinence over moderation. In less than nine months no fewer than 150,000 names were enrolled as taking the Pledge. It rapidly spread to Limerick and elsewhere, and some idea of its popularity may be formed from the fact that at Nenagh 20,000 persons are said to have taken the pledge in one day, 100,000 at Galway in two days, and 70,000 in Dublin in five days. At its height, just before the Great Famine of 1845-48, his movement enrolled some 3 million people, or more than half of the adult population of Ireland. In 1844 he visited Liverpool, Manchester and London with almost equal success.
However, his campaign did have the unforeseen consequence of an increase in ether consumption (much more dangerous than alcohol) by those seeking intoxication but not willing to break their pledge.
For two years, despite grave illness, Father Mathew blazed a trail of success across the United States. Boston, Philadelphia, Cincinnati, Little Rock, New Orleans, and many places in Florida, Georgia, Tennessee, Virginia, Delaware and other areas heard his exhortations and were won to the practice of total abstinence. Everywhere there were crowds and enthusiastic receptions.
When he left the USA in 1851, strong temperance societies carried on the work. “I thank heaven I have been instrumental in adding to the ranks of temperance over 600,000 in the United States,” he wrote. Mathew has a statue dedicated to him in Salem, Massachusetts.
Mathew, a high-profile visitor to the USA, found himself at the centre of the Abolitionist debate. Many of his hosts were pro-slavery, and wanted assurances that their influential guest would not stray outside his remit of battling alcohol consumption. But Mathew had signed a petition against human bondage in 1842 when he had hosted former slave Frederick Douglass in his Cork home. Now however, in order to avoid upsetting his powerful American friends, he snubbed an invitation to publicly endorse Abolition, sacrificing his friendship with that movement.