There is a mathematical style in which proofs are presented as strings of unmotivated tricks that miraculously do the job, but we found greater intellectual satisfaction in showing how each next step in the argument, if not actually forced, is at least something sweetly reasonable to try. Another reason for avoiding [pulling] rabbits [out of the magicians's hat] as much as possible was that we did not want to teach proofs, we wanted to teach proof design. Eventually, expelling rabbits became another joy of my professional life.

-- Edsger Dijkstra

Edit: Added context to "rabbits" in brackets.