I would have thought ταύτῃ τῇ πέτρᾳ must refer to Πέτρος, I don't see any other antecedent in view. I would have thought the change in gender was simply because the name of a man would be in a masculine form, and that this is sufficient to explain the difference in the two words.Matthew 16:18 wrote:κἀγὼ δέ σοι λέγω ὅτι σὺ εἶ Πέτρος, καὶ ἐπὶ ταύτῃ τῇ πέτρᾳ οἰκοδομήσω μου τὴν ἐκκλησίαν
Many interpreters say roughly that Πέτρος refers to a stone, not a rock, and that πέτρᾳ refers to bedrock. I've also seen the claim that both words have a wide range of meanings, and in the Hellenistic era πέτρᾳ means bedrock and πἑτρος is no longer really used to refer to a stone.
Can anyone help me sort this out while I sit here without my books?