Frankl often uses ethos (appeal to credibility) across both parts of Man’s Search for Meaning in order to present himself as one uniquely well-equipped to make the case for logotherapy.
He begins Part I of the book with his primary aim: to attempt a methodical (that is, scientific) presentation of life during the Holocaust but with the intimate knowledge of the “insider.” He explains why being a former prisoner himself offers a rare perspective which differs from a factual account:
Here, facts will be significant only as far as they are part of a man's experiences. It is the exact nature of these experiences that the following essay will attempt to describe. For those who have been inmates in a camp, it will attempt to explain their experiences in the light of present-day knowledge.
In this passage, Frankl uses ethos to explain to the reader why his perspective as both a scientist dedicated to empirical truth and a former prisoner with intimate experience validates his views on logotherapy. His psychotherapeutic doctrine, which combines observable fact with a deep knowledge of the human condition, remains best argued by one with both the scientific training to draw general conclusions from observation and the rare insight of having personally suffered these horrors.