Talk:Scathach/@comment-33126314-20171010204509/@comment-28209103-20171106225859

@Sibayans : Technically it's possible to summon someone as long as he's already died, however summoning someone from the future are harder than it seems because you need a catalyst and finding catalyst for someone in the future are extremely unlikely.

Rin are just lucky that he got that pedant which is the catalyst for King of Butler thus it's possible to summon someone in the future. Merlin utilize that rule as he summoned himself before he was even born so technically he's not alive but neither he's dead.

and finally the main reason why EMIYA are different from the other heroic spirit is that he's a counter guardian which means at some point he sold his soul to the world. Similarly to how Saber are able to be summoned as heroic spirit while she's technically still not dead yet because she made a pact to the world probably it's possible to summon EMIYA as separate completely separate entity from Shirou Emiya due to 2 reason : 1. Counter Guardian or contractor of 'Gaia' might be exception of the rule, or 2. EMIYA are not considered to be the same person as Shirou, as a fact Shirou will never become EMIYA, basically a what-if possibility.