The sum of all knowledge
On the wonderful thing that is the www, and his introduction to it (I didn't notice who the author was until the end!).
I sometimes forget how shielded I am for the ad-covered dumpster fire that is many pages; either from blocking them or not visiting them. Enjoyed the upsides he mentioned: easy to contact the author of something, cross-referencing without stacks of books, and the ability to pulish things yourself.
Try to verify things you read (lies are rampant online, fact-checking is easier than ever!), write and contribute things, stay out the political trench fights.