At this time the Millerite or Adventist movement was growing, and in 1843 Thomas was introduced to William Miller, the leader of the Millerites. He admired their willingness to question orthodox beliefs and agreed with their belief in the second coming of Christ and the founding of a millennial age upon His return. Thomas continued his studies of the Bible and in 1846 travelled to New York, where he gave a series of lectures covering 30 doctrinal subjects that later formed part of his book "Elpis Israel" (The Hope of Israel).