Every Doctor has those moments that define him. That reveal him, his values and ideals. That show he’s worthy of the name.
Of course, they’re also the moments where the actors prove themselves worthy. William Hartnell letting go of his only family. Tom Baker asking “Do I have the right?” David Tennant wrestling with his conscience so many times.
Peter Capaldi’s first series, of course, gave us a perfect I Am The Doctor moment with that speech in “Flatline.” It was that stand-up-and-squee moment we’d been waiting for all season, and for a little while it might have been the Twelfth Doctor’s defining moment.
Until now. Until a scene so powerful, a performance so perfect, that Capaldi needs only three words to break your heart.