Quite a few different translations of the song title are possible and have been made. Hard to tell which one is the best.
My personal favourite would be “Pure reason may never prevail”…
what I remain a bit uncomfortable with is that ‘Pure Reason’ sounds a bit too Kantian to me, i.e. like it were a translation of ‘Reine Vernunft’. But it remains the best sounding translation I’ve seen.
“Being purely sensible” is really awkward (though valid) phrasing in common conversational English… “Pure reason must not prevail” works best poetically, with its near iambic rhythm.
Pure reason sounds a little off to me so I suggest sheer reason instead,that is seems to be more to the point of the German, so all in all I am a bit undecided between sheer reason must never prevail and sheer reason may never prevail but I thinkthe second one is closest to it