  It is firmly believed that a signal of neutrinoless double beta decay can
unquestionably confirm the Majorana nature of neutrinos. However we notice that
a Majorana neutrino mass induced after some neutrinoless double beta decay
processes can be accidentally cancelled by another Majorana neutrino mass
induced before any neutrinoless double beta decay processes. This realistic
cancellation can simultaneously allow an observable neutrinoless double beta
decay and a vanishing Majorana neutrino mass. In consequence a future discovery
of neutrinoless double beta decay cannot fully rule out the possibility of
Dirac neutrinos.
