Ignorance is the binding factor in the development of ego, but it also has a subtle relationship with the basic intelligence of buddha nature. Ignorance is not solid but is based on sparks or flashes of ignorance operating on some ground. Between two sparks of ignorance is the ground of intelligence on which this process of ignorance is operating. Sometimes, ignorance forgets for a moment to maintain itself, so that the awakened state comes through. So a meditative state of mind occurs spontaneously when, occasionally, the efficiency of ego’s administration breaks down.
From Glimpses of Abhidharma by Chögyam Trungpa, pages 57-58.