The purpose of this paper is to clarify the Cambridge Platonists' idea of liberty as an underlying concept both in theory and practice, by paying attention  to their mode of thinking aimed at reconciling the reason of religion with that of the world, or morals with institutions. Through this, I hope to show the  moral significance as well as the moral force of the term "liberty" proposed from the theological intellectualist tradition in early modern English thought.  This paper also addresses the question of divine providence and freewill in the light of "participation", another characteristic idea of the Cambridge  school on human engagement with God. By focusing on the conception of the temporal sphere that implements this engagement, I shall emphasise the  intimate connections between the speculative and the practical, and contemplation and action.
 The paper begins by examining the Platonic philosophical defence of free will, and then proceeds to the discussion on supernatural "Christian liberty",  regarding it as a transformation from natural "freedom from necessity" to spiritual "freedom from sin" and "toward God". Furthermore, it will attempt to  grasp several key subjects related to the Cambridge Platonists' institutional viewpoint in church and state. These are the ideas of temporal order, church  government, freedom of conscience and Christian polity, all constituting a coherent idea-world of freedom and participation in the Cambridge Platonists.
 In conclusion, the paper returns to the discussion on God the original and eternal idea, who effects the realisation of liberty and salvation through some  cooperative works in history, where the appropriate moral preparation for an afterlife by temporal institution is necessitated.