Chaplaincy is institutional in shape, ministry that follows an institution rather than a parish, but that alone says nothing about how a modern chaplain is actually trained. That training has a specific origin. Anton Boisen, a Presbyterian minister who had himself been hospitalized for psychiatric illness, argued after his recovery that ministers preparing for institutional chaplaincy learned far too little from classroom theology and far too little from direct encounter with the people they would serve. In 1925, at Worcester State Hospital in Massachusetts, he placed seminary students directly on the wards to learn from what he called the living human document, the patient's own experience, read with the same seriousness a seminarian was trained to read scripture.
The approach grew into Clinical Pastoral Education, commonly called CPE, structured programs combining supervised ministry with group reflection on the minister's own reactions to suffering, and it spread from psychiatric hospitals into general hospitals, prisons and the military. CPE is no longer a Presbyterian innovation confined to one denomination. Certification bodies for professional chaplains across multiple faiths, in hospitals, hospices, prisons and the armed forces, now require a set number of completed CPE units before a chaplain can be credentialed at all, so Boisen's insistence on learning from the patient rather than only from the textbook became the actual gate a person has to pass through to hold the job of institutional chaplain.