Because, even if you doubt the veracity of that passage from Matthew’s gospel, or do not doubt it but see no divinity in the person of Christ, and thus do not attribute to it the power it might otherwise have, and perhaps even regard it as some sort of fraudulence, or, at best, a genuine sentiment that has been misconstrued, you should still be able to find in it the shape of the rationale by which the Church, responding to it, attempts to manifest in time.