Archer's True Motivations.

Obviously Unlimited Blade Works spoilers but also slight Fate and Heaven's Feel spoilers as well.

If you ask any Fate/Stay Night fan about Archer's goals and motivations, they will most likely answer that his main goal is to kill Shirou, his past self, in order to erase his exitance as a Counter Guardian, and well, that's not entirely wrong

But I believe that that is only a surface level reading of his character, and that there is plenty of evidence across all 3 routes of Fate/Stay Night that his true motivation, perhaps one that he is not even consciously aware of himself, goes deeper than that.

So to start with, here's why I don't think Archer TRULY wanted to kill Shirou, well, to put it simply, he had way too many opportunities to do it, and yet he did not, if killing Shirou was, as he put it, the only reason he was able to preserve and struggle, then-

-he had absolutely no reason to hesitate to do it during any of their conversations in the Fate and Heaven's Feel Routes, or even during the confrontation with Caster in UBW, but he did not, it was not more important than what was going on at the time.

Which seems odd to me considering Archer made it sound like it was literally the only thing he cares about anymore. Yes he does attack him at the end of the Caster battle, but that was because Shirou provoked him way too much, and even then he was doing a bad job at killing him.

Another thing to take into account, Saber herself explains that Archer must know that him killing Shirou has a 0% chance of affecting anything regarding him

And he admits that he knows that it's most likely impossible, but says that he doesn't care and as long as he gets to release his pent up frustration on his younger self, he's fine, and here I think lies a truth that even Archer was subconsciously hiding

That what he truly wanted wasn't a chance to kill Shirou, but rather a full on confrontation with his younger self, a confrontation that won't end with him killing Shirou instantly, but one where their ideals and wills can clash

Hence he waited until he was at his weakest and Shirou was at his strongest(well, besides being unable to use UBW), and even THEN, Archer could've still won that fight relatively easily if he went for the kill from the start, or, as he thinks himself, if he went into long range.

But see, that would've been the same thing as admitting defeat against Shirou, that he could only win because he was more skilled, not because his beliefs and will are stronger and more correct compared to Shirou's

Beyond that, I believe that very deep inside his heart, behind all the anger, hatred, and regret, Archer *wanted* to be proven wrong, he wanted to confront his younger self and still lose, because Archer wasn't convinced that his way was wrong, he was just lost

He lost sight of what his original ideal was, and believed that it might've all been a mistake, but he needed to confront his younger self to receive an answer, whether that answer was "I was wrong" or "But still, I was not wrong", he just wanted an answer to erase his doubts

And deep down, I truly believe that he wanted it to be the latter answer rather than the former, that is why he was able to smile at the end of it all and claim that he was not wrong after all.