Should I learn an opening or should I first study it?

Some clever advice from Bill Hartston in "Teach Yourself Better Chess". He says to choose an opening, play through high level games where you identify with the moves from one side or the other. Having done that, then play through a larger collection of games in that opening (at least 10 and as many as 100), until you correctly guess the vast majority of moves. Then, and only then, do you hit the books, to see what 'theory' says.
He equates it with learning a foreign language, with each game extending your vocabulary!