Years ago, walking across a beautiful wooded college campus in the Northwest, I had a conversation with a friend about Yeats' notions of will and imagination. My friend suggested that imagination was a middle term and that will represented one extreme, which left us missing a term. (This was long enough ago that one might make structuralist arguments, not post-structuralist ones!) We came up with a sort of jokey formulation: will we represented in our system as a "fascist" for whom control was paramount and the opposite of will as a "hippie," for whom any control was anathema. In the middle, we decided, there was playfulness--what Yeats called "imagination."
The plumbline, even when it is perfectly still, only does its job because it is free to move; conversely, it is constrained by the laws of physics to come to rest over a point of equilibrium, drawing a line straight through the center of the earth. In a physical or mechanical system, we say there is "play" if there is a bit of slack or looseness, enough to allow some unpredictable motion without becoming completely random; if there is no play in the system, it locks up. So this is just one more metaphor for the middle way, but a useful one for me. At my best, such an approach governs my approach to daily life, as well as to poetry. The state of play is akin to what a Buddhist might simply call being awake.