Saint Arnold Janssen was born on November 5, 1837 in Goch, Germany. Arnold was the product of a middle-class environment. He was able to pursue higher studies because the curet Father Ruiter, took a personal interest in him. During his years at the Diocesian Minor Seminary the study of languages caused him great difficulties.
As a consequence he had little time left for his favorite subject-mathematics. However, by dint of persevering effort he became proficient enough to pass the final language examinations satisfactorily. Later on he was able to express himself adequately both in Latin and in French. He desired to become a priest and, indeed, a priest professor of mathematics and the natural science. This pleased his bishop very much because there were many Catholic schools in the diocese. He was soon one of the most diligent of the students. For his fellow-students he was both a source of strength and a protection amid the dangers of the liberal university of Bonn.
In three and a half years he earned a State Teacher's Certificate and was invited to teach at a secondary school in Berlin. This invitation, however, he turned down. He was not yet 24 years old when he completed his theological studies and was ordained priest (15 August 1861). But already he had acquired a solid professional training and had a well-formed character. He worked conscientiously and used all his time and energy for the tasks entrusted to him.
This sense of conscientious resposibility characterized the 12 years of his educational work in Bocholt. To his efforts to improve the new school, his activity as both a lecturer and a writer must be added. Under the influence of his study of the theology of St. Thomas Aquinas and the speculative works of the young professor of Cologne, Joseph Matthias Scheeben, his own piety was deepened. It became theocentric and, indeed, markedly trinitarian in character. Just as he had schooled himself in strict ecclesiastical theologians, so his whole attitude was characterized by loyalty to Rome.
When, during the 1st Vatican Council, the clergy of Bocholt, in line with the opinion common in Germany, spoke out against the opportuneness of the dogma of papal infallibility, Arnold Janssen was alone in aligning himself with the Council majority. The incident is proof both of his intellectual independence and his self-reliance.