Warning: This page contains major spoilers for Harry Potter and the Half-Blood Prince.

The Lazy Man’s Guide to Defending Snape: (AKA the condensed version of the evidence)

1. Dumbledore is not an idiot

Almost all of the “Snape is Good” arguments can be summed up in these five simple words: “Dumbledore is not an idiot.” Dumbledore is a powerful wizard who would not trust Snape without a very good reason. To believe that Snape is evil is to believe that Dumbledore is a fool.

2. There are parallels in language throughout the book (or didn’t I just read that?)

This is not reality. JKR is not simply transcribing what anyone has actually said. Every line is crafted for a reason. There seem to be obvious similarities between certain scenes (see the extended evidence page for specific examples: Dumbledore’s words to Harry just before they go to the Cave, Dumbledore’s potion-induced ravings, parallels between the Cave scene and the Tower scene: hatred & revulsion, Dumbledore makes Harry promise...)

3. For an evil guy, Snape wasn’t all that evil.

Snape kills no one else on his way out of Hogwarts even though not everyone had taken felix felicis. Snape didn’t kill Flitwick even though he clearly had the opportunity. Snape doesn’t ever fully attack Harry. He blocks spells, gives advice, stops Crucio, and he doesn’t take Harry with him.

4. JKR compares Snape to Fang (after Harry calls him a coward)

Why would Rowling use the analogy of the dog trapped in a burning house unless we are supposed to think of Snape in a similar way? Snape, here, is not ecstatic as he should be after killing someone he hated and had to obey all this time. Instead, he is in pain, and he reacts harshly to the word coward because what he was forced to do took a great amount of effort and bravery and has cost him a lot. His world is collapsing around him. The comparison to Fang is purposeful on Rowling's part - Snape had no other option. There is no good reason to compare Snape to a beloved pet trapped in a burning house if he is evil.

5. The simplest explanation is that you can’t use Occam’s razor in literature or entertainment (or Occam’s razor doesn’t make a very exciting story - see Cold Creek Manor.)

Literature is not reality - a more complex story is more interesting. If you could figure it out from Chapter one, you wouldn’t sell many books. Certainly we have to believe that a 7 part series is going to have a lot of twists and turns. “Snape is evil” is much too simple and it ignores a lot of evidence from previous books. Even Scooby Doo had twists.

6. The message of books

If Snape is evil, the message becomes something like “well, boys and girls, the moral of this story is everyone will betray you - trust no one - not even your parents - your best friends - or your teachers - and especially not the trusting old wizard mentor guy - he’s just old and doesn’t know what he’s doing.” Do you really believe JKR is trying to say that trusting people is a weakness? What a happy story! In order to have love you must have trust and it’s pretty obvious that love is an important component to defeating evil.

7. Fawkes didn’t save Dumbledore (or Fawkes takes a holiday)

Are we really supposed to believe that Dumbledore’s big red bird decided he would rather stay at home than be loyal when Dumbledore was killed? Did he develop temporary amnesia and forget that he can eat AK curses for breakfast? Rowling clearly introduced this ability of Fawkes’ for a purpose in OotP and we cannot just forget it one book later. Perhaps this time, he didn't come to the rescue because he was told not to.

8. Snape doesn’t have an evil monologue (or the art of evil exposition)

Quirrel, Tom Riddle (in the diary), faux-Moody, Umbridge, and Draco all have moments where they explain the brilliance of their evil plans. It’s what villians do. At the tower scene, Snape kills Dumbledore very suddenly without any speech or anything. If Snape were actually evil all along, I would have expected him to stand in front of the weakened Dumbledore, relishing this moment, announcing that he alone was able to fool the mighty Dumbledore, etc.

9. Felix Felicis

If Snape was indeed evil, the potion should have coaxed Hermione, etc. into doing SOMETHING to delay Snape at least and it didn’t. This leads to the conclusion that the lucky thing to do was to let Snape succeed because he’s still working for the good side.

Note: See the old, extended version of the evidence page for quotes, references etc.