Where the Heart Beats

I'm reading an interesting book by Kay Larson, a biography of John Cage, Where the Heart Beats: Zen Buddhism, and the Inner Life of Artists. (Penguin 2012)  She includes an interesting quote from John Cage:  "What can be analyzed in my work, or criticized, are the questions I ask."

If one were to apply this to one's own work, it brings up interesting things.  One of the observations that others have had in my writing are shifts in verb tense: past and present.  I do have a question about time. Although some people declare, the past is the past - it is behind us - isn't the present made up of both here/now and memory?