Near the end of the talk someone asks you how to delete data if the state of the machine is just a function of the network packets it has received.

I have to admit I didn't really understand your answer:

> [When you try to forget data] you're making a subset of this computer that will not compute when it tries to use this information.

Could you elaborate a little on what that means, and how you'd apply it in practice. If I wanted to not just make data inaccessible but actually purge it from my machine, how would I do so?