Computation --- well-defined sequences of state changes --- is universal. In this talk, we discuss recent struggles with understanding three aspects of it: (1) How does the brain create, recall and associate memories? (will you remember this abstract?)  (2) How to measure the complexity of human computation? (think adding in your head or playing chess) and (3) What concepts/functions can (and cannot) be provably learned by deep neural networks? (this one might be worth some $$). They all have a common answer --- I don't know.  I'll describe some surprises, several hypotheses and a sea of challenges.