This dissertation examines the historical and philosophical background of the initial evidence doctrine in North American Pentecostal churches. It begins by reviewing the philosophy of Thomas Reid, known as Scottish Common Sense Realism, and shows how this philosophy became the predominant philosophy in the United States throughout the nineteenth century. The emphasis on sensory evidence for a work of God in the life of a believer became a paradigm that pre-Pentecostals and Pentecostals adopted and allowed them first to search for, and then accept a physical evidence for the Baptism in the Holy Spirit. One of the main ways in which Scottish Common Sense Realism was communicated, both as a method and a vocabulary to the nineteenth century church was through what has been called the "Christian Evidences" literature. With its emphasis on prophecy and miracles as well as the importance of inner experience, the Christian evidences provided both the method and vocabulary for the early Pentecostals in their search for physical evidence of the sought for Baptism in the Holy Spirit. The importance of physical expressions when the Spirit of God was present was modeled and encouraged throughout the nineteenth century in the Camp Meetings that were so ubiquitous. This was true not only of the church as a whole in the early part of the century, but of the holiness arm of the church, out of which the Pentecostals came, in the last third of the century. The sense of urgency to discover an acceptable evidence of the Baptism in the Holy Spirit was provided in large part by the premillennialism so common in parts of the church in the last half of the nineteenth century - the parts out of which Pentecostalism came. This included the importance of the work of the Spirit in evangelism and the Biblicism so common in the premillenial movement. The last contributor to the search for a physical evidence of the Baptism in the Holy Spirit and the acceptance of the initial evidence doctrine was the extensive restorationism in the North American church. Restorationism suggested that any acceptable Since speaking in tongues was the only consistently reported physical evidence in Acts, this restorationist outlook virtually demanded that it would become the accepted evidence. The dissertation ends with a summary of the initial evidence doctrine from its origin in Topeka, Kansas in 1901 to its widespread acceptance within less than 20 years.