Allen met Thomas Young when he moved to Salisbury, a doctor living and practicing just across the provincial boundary in New York. Young taught him a great deal about philosophy and political theory, while Allen shared his appreciation of nature and life on the frontier with Young. They eventually decided to collaborate on a book intended as an attack on organized religion, as Young had convinced Allen to become a Deist. They worked on the manuscript until 1764, when Young moved away from the area taking the manuscript with him. Allen recovered the manuscript many years later, after Young's death. He expanded and reworked the material, and eventually published it as "Reason: the Only Oracle of Man".