Title: Oracles Are Subtle But Not Malicious Scott Aaronson Institute for Advanced Study (IAS) Abstract: I'll first review the concept of an oracle, and why it plays such a central role in the P/NP question and in theoretical computer science more generally. I'll then survey the slim progress that's been made so far toward proving nonrelativizing lower bounds. Finally I'll present a new result: that there exists an oracle relative to which the computational complexity class PP (Probabilistic Polynomial-Time) has linear-size circuits. The reason this is interesting is that Vinodchandran showed, via a nonrelativizing argument, that PP does *not* have circuits of size n^k for any fixed k. Indeed I've extended Vinodchandran's result, to show that PP does not even have quantum circuits of size n^k with quantum advice. Prerequisites: You don't need to understand http://www.complexityzoo.com; you just need to be able to stare at it for at least 15 seconds without screaming in terror. More details: http://arxiv.org/abs/cs.CC/0504048 Notes for a related talk: http://www.scottaaronson.com/talks/subtletalk.pdf