Born at Kempen in the Diocese of Cologne, about 1379, he died July 25, 1471.
His parents, John and Gertrude Haemerken, were of the artisan class; it is said that Gertrude kept the village school, and most probably the father worked in metals, a common calling in Kempen, whence perhaps the surname Haemerken, or Haemerlein, Latinized Malleolus (a little hammer). We have certain information of only two children, John, the senior by about fourteen years, and Thomas. Thomas was only thirteen when he set out for the schools of Deventer, in Holland. His brother had preceded him thither by ten or twelve years, and doubtless Thomas expected to find him still there. On his arrival, however, he learned that he had gone two years since with five other brothers of the Common Life to lay the foundations of a new congregation of Canons Regular at Windesheim, about twenty miles from Deventer, where he then went and was lovingly received by his brother who provided him with a letter of introduction to the superior of the Brothers of the Common Life at Deventer, Florentius Radewyn. Radewyn gave a warm welcome to the young brother of John Haemerken of Kempen, placed him for the time being in the house and under the maternal care of "a certain noble and devout lady", presented him to the rector of the schools, and paid his first fees, though the master returned the money when he learned whence it came. These particulars we have from the pen of Thomas himself in the biographies, written in his old age, of Gerard Groote, Florentius Radewyn, and their followers (see "The Founders of the New Devotion", London, 1905). For seven years he remained at Deventer, numbered from the first among the disciples of Radewyn, and for a good portion of the time living in his house under his immediate care. It is impossible to exaggerate the influence of those years in the formation of his character. The "new devotion", of which Deventer was then the focus and center, was a revival in the Low Countries in the fourteenth cetury of the fervour of the primitive Christians at Jerusalem and Antioch in the first. It owed its inception to the fervid preaching of the Deacon Gerard Groote, its further organization to the prudence and generous devotedness of Florentius Radewyn. Its associates were called the "Devout Brothers and Sisters", also the "Brothers and Sisters of the Common Life". They took no vows, but lived a life of poverty, chastity, and obedience, as far as was compatible with their state, some in their own homes and others, especially clerics, in community. They were forbidden to beg, but all were expected to earn their living by the labour of their hands; for the clerics this meant chiefly the transcribing of books and the instruction of the young. All earnings were placed in a common fund, at the disposal of the superior; the one ambition of all was to emulate the life and virtues of the first Christians, especially in the love of God and the neighbour, in simplicity, humility, and devotion. Furthermore, partly to provide the Devout Brothers and Sisters with effective protectors and experienced guides, partly to afford an easy transit to the religious state proper for those of their number who should desire it, Gerard Groote conceived the idea of establishing a branch of the canonical order, which should always maintain the closest relations with the members of the new devotion. This scheme was carried into effect after his untimely death, at the early age of forty-three, by the foundation of the congregation of Windesheim, as it was afterwards called from the tract of land where the first priory was established (1386). These details are given as helpful to a better understanding of the life and character of à Kempis, a typical and exemplary Brother, and for seventy-two years he was one of the most distinguished of the Canons Regular.
At Deventer Thomas proved an apt pupil, already noted for his neatness and skill in transcribing manuscripts. This was a life-long labour of love with him; in addition to his own compositions he copied numerous treatises from the Fathers, especially St. Bernard, a Missal for the use of his community, and the whole Bible in four large volumes still extant. After completing his humanities at Deventer, in the autumn of 1399, with the commendation of his superior, Florentius Radewyn, Thomas sought admission among the Canons Regular of Windesheim at Mount St. Agnes, near Zwolle, of which monastery his brother John was then prior. The house had been established only the previous year, and as yet there was no claustral buildings, no garden, no benefactors, no funds. During his term of office, which lasted nine years, John à Kempis built the priory and commenced the church. In these circumstances we find the explanation of the fact that Thomas was not clothed as a novice until 1406, at which date the cloister was just completed, nor ordained priest until 1413, the year after the church was consecrated. He was twice elected subprior, and once he was made procurator. The reason assigned by an ancient biographer for the latter appointment is one that does honour both to Thomas and his brethren, his love for the poor. After a time his preference for retirement, literary work, and contemplation prevailed with the Canons to relieve him of the burden. The experience thus gained he made use of in a spiritual treatise, "De fideli dispensatore".
His first tenure of office as subprior was interrupted by the exile of the community from Agnetenberg (1429), occasioned by the unpopular observance of the Canons of Windesheim of an interdict laid upon the country by Martin V. A dispute had arisen in connection with an appointment to the vacant See of Utrecht and an interdict was upon the land. The Canons remained in exile until the question was settled (1432). The community of Mount St. Agnes had dwelt meanwhile in a canonry of Lunenkerk, which they reformed and affiliated to Windesheim. More than a year of this trying period Thomas spent with his brother John in the convent of Bethany, near Arnheim, where he had been sent to assist and comfort his brother, who was ailing. He remained until his death (November, 1432). We find record of his election as subprior again in 1448, and doubtless he remained in office until age and infirmity procured him release. It was part of the subprior's duties to train the young religious, and to this fact no doubt we owe most of his minor treatises, in particular his "Sermons to the Novices Regular". We also know from early biographers that Thomas frequently preached in the church attached to the priory. Two similar series of these sermons are extant ("Prayers and Meditations on the Life of Christ" and "The Incarnation and Life of Our Lord", London, 1904, 1907). They treat of à Kempis' favorite subjects, the mystery of our Redemption, and the love of Jesus Christ as shown in His words and works, but especially in the sufferings of His Passion. In person Thomas is described as a man of middle height and slight of build, dark complexion and vivid coloring, with a broad forehead and piercing eyes; kind and affable towards all, especially the sorrowful and the afflicted; constantly engaged in his favorite occupations of reading, writing, or prayer; in time of recreation for the most part silent and recollected, finding it difficult even to express an opinion on matters of mundane interest, but pouring out a ready torrent of eloquence when the conversation turned on God or the concerns of the soul. At such times often he would excuse himself, "My brethren", he would say, "I must go: Someone is waiting to converse with me in my cell." A possibly authentic portrait, preserved at Gertruidenberg, bears as his motto the words: "In omnibus requiem quaesivi et nusquam inveni nisi in een Hoecken met een Boecken" (Everywhere I have sought rest and found it nowhere, save in little nooks with little books). He was laid to rest in the eastern cloister in a spot carefully noted by the continuator of his chronicle. Two centuries after the Reformation, during which the priory was destroyed, the holy remains were transferred to Zwolle and enclosed in a handsome reliquary by Maximilian Hendrik, Prince-Bishop of Cologne. At present they are enshrined in St. Michael's Church, Zwolle, in a magnificent monument erected in 1897 by subscriptions from all over the world and inscribed: "Honori, non memoriae Thomae Kempensis, cujus nomen perennius quam monumentum" (To the honor not to the memory of Thomas à Kempis, whose name is more enduring than any monument). The same Maximilian Hendrik, who showed such zeal in preserving and honoring the relics of à Kempis, was also eager to see the cause of his beatification introduced and began to collect the necessary documents; but little more than a beginning was made when he died (1688) and since that date no further steps have been taken.