Such apparently unreasonable behavior is often in the service of reason, since it aims at the empirical authentication of religious doctrine. In fact, even the most extreme expressions of faith are often perfectly rational, given the requisite beliefs. Take the snake-dancing Pentecostals as the most colorful example: in an effort to demonstrate both their faith in the literal word of the Bible (in this case Mark 16:18) and its truth, they "take up serpents" (various species of rattlesnakes) and "drink any deadly thing" (generally strychnine) and test prophecy ("it shall not hurt them") to their heart's content. Some of them die in the process, of course, as did their founder, George Hensley (of snake bite, in 1955)—proof, we can be sure, not of the weakness of their faith but of the occasional efficacy of rattlesnake venom and strychnine as poisons.