(Spirit Rock Meditation Center) We review some of the main themes from last week's talk on developing concentration (samadhi), including the importance of such practice for the Buddha and his teachings; without samadhi, the Buddha says, there is no freedom. We examine ways of practicing (including outside of formal meditation) and look at some of the factors that indicate a deepening of samadhi (the jhanic factors). We then review the main challenges of developing samadhi, particularly over-active minds, sleepiness and low energy, and over-efforting. We also explore further challenges to the development of samadhi, including working with background thoughts, the ways that more unconscious material can surface in cultivating samadhi, and attachment to concentrated states. The talk is followed by discussion.