Kavanagh, James Blake (1822–86), priest, nationalist, and philosophical and scientific writer, was born in Kilballyowen, in the parish of Killaveny, Co. Wicklow, son of Thomas Kavanagh and Mary Kavanagh (née McDonald). He received his early education at St Peter's College, Wexford, where he displayed a strong passion for scientific studies. In 1839 he entered Maynooth. He was ordained (1844) and appointed professor of rhetoric at St Patrick's College, Carlow (1850). After a year on a mission to the diocese of Ferns (1853), he returned to Carlow, where he became dean of the ecclesiastical college. He was appointed professor of moral philosophy in 1853 and professor of mental philosophy in the following year. In 1862 he became vice-president and professor of theology at St Patrick's. He served as president (1864–80) and as parish priest of Kildare and Rathangan becoming closely involved in local political and social issues. On his arrival at Kildare he joined the local branch of the Land League and acted as intermediary between landlords and tenants, most notably in disputes on the estate of the duke of Leinster (qv).
He was intimately involved in the Kildare waterworks scheme and proposed a scheme for lighting Kildare town with electricity. At the time of his death he was organising a company to this end. He helped instigate many local projects such as the county infirmary, new schools for the Christian Brothers, a public hall, and the restoration of the church of St Brigid. Deeply concerned with the intellectual resources of Irish catholics, in 1869 he launched the Carlow College Magazine ‘to show to the world what catholic Irishmen can do to raise the undeniably too low tone of their national literature’. The magazine contained articles on literature, philosophy, politics, science, poetry, and art. It was attacked by W. G. Ward (1812–82), editor of the Dublin Review, in 1869 for encouraging the study of modern philosophy and was further condemned by Cardinal Paul Cullen (qv) for serialising a novel by William Carleton (qv), The red-haired man's wife. The magazine ceased publication in 1870.
Kavanagh was a skilful and lucid scientific lecturer. Although containing little original research, his published lectures Solar physics (1877) and Comets and meteors (1877) were well received and popular. At the Dublin meeting of the British Association in 1878, he refused an honorary degree from the University of Dublin. His Reply to Mr Gladstone's Vaticanism (1875) criticised the liberal leader's assertion that the doctrine of papal infallibility would breed sedition, though he remained an admirer of Gladstone. In 1880 he was named as one of the senators of the RUI. In 1885 he wrote a defence of the RUI's examination paper in metaphysics, which had been criticised by members of the hierarchy as being unfair to catholic students and containing ‘anti-Christian’ works. His Study of mental philosophy by catholic students in the RUI (1885) argued that the church should engage with, rather than ignore, the challenge of modern science and philosophy.
He died while saying mass on 6 October 1886 in the parish church of St Brigid when an 18-in. marble figure of an angel fell from the canopy above the altar and struck him, causing him to fall and strike his head fatally on the altar steps. Ironically, he himself had designed the altar, ignoring the advice of the local architect. W. B. Yeats (qv) remarked that his death ‘made the awe-struck peasantry see an event unearthly and tremendous’. He was survived by his two brothers, one of whom, Michael, was the president of St Peter's College, Wexford.