Did C. S. Lewis write The Dark Tower?: An Examination of the Small-Sample Properties of the Thisted-Efron Tests of Authorship

The Dark Tower is a fragment of a science fiction novel, attributed to C.S. Lewis and published posthumously. Shortly after its publication controversy arose, questioning the work's provenance and authenticity. This controversy still continues. We apply and extend procedures developed by Thisted and Efron (1987) to investigate whether word usage in The Dark Tower is similar to that in Out of the Silent Planet and Perelandra, two works of the same genre and period known to be by Lewis. We further examine the validity and limitations of these procedures in the case at hand. Our results show vocabulary usage in The Dark Tower differs from that predicted by the baseline Lewis works.