I have emailed this question to several friends, but have received surprisingly (or unsurprisingly) few responses.
I have been a Protestant my entire life, yet I acknowledge what R.R. Reno described as "the insanity of [the] slide into self-guidance." (Catholic Matters, Richard John Neuhaus, p. 65). I also whole-heartedly agree with Neuhaus himself when he says, "The allegedly autonomous self who acknowledges no authority but himself is abjectly captive to the authority of the Enlightenment rationality that finally collapses into incoherence." He adds, "Confronted by such truth claims, we necessarily ask, 'Sez who?' By what authority, by whose authority, should I credit such claims to be true?" (ibid., p. 70)
And so I ask: If you are Protestant, why are you Protestant and why are you not Catholic or Orthodox? If you are Catholic, why are you Catholic and not Protestant or Orthodox? If you are Orthodox, why are you Orthodox and not Protestant or Catholic?
Note that whatever question applies to you is actually in two parts, asking a positive affirmation of why you are what you are and an answer of why you are not what you are not.
Thanks in advance to all who search deeply and share good, honest thoughts.