And what purpose would it serve? What rational motive could we have for such a deception? I, in particular, stand only to lose. If you accept that he's your biological father, I run the risk of you rejecting me as your father.

[Ferran will try to throw logic and self-interest at Shaun and see if it works. If Shaun will accept that this really is Riley, he'll likely accept the rest of it, too. As Zetta said, there aren't any better explanations to account for Riley returning from the dead.]