William Law is best remembered today for his Serious Call to a Devout and Holy Life. To those interested in his spirituality, however, other works have greater impact, in particular The Spirit of Prayer and The Spirit of Love, which are considered the finest and most appealing. In the years in which they were written, his vision had reached its fullest and most characteristic development, and his literary power was at its height. It is in these books that the profound influence of Jacob Boehme can be most clearly seen. His great synthesis of the mystical outpourings and orthodox Christian theology, provide an English spiritual classic. Law's understanding and interpretation of mysticism was more original than traditional, being dynamic and creative. He believed in the life of God working from within, and the flame of divine love being a link with and an understanding of God. He conceived that mysticism was a matter of life, that relied on willing rather than knowing, and that ultimately rested on trust in God. Despite holding no official position he was widely regarded in his own time and later as a spiritual guide, and his trilogy The Spirit of Prayer, The Spirit of Love and The Way to Divine Knowledge was the mature expression of his theology and religion.

'It is not to be thought that the life of darkness is sunk in misery and lost as if in sorrow. There is no sorrowing. For sorrowing is a thing swallowed up in death, and death and dying are the very life of the darkness.' Jacob Boehme's mystical pantheism and dialectical conception of God - in which good and evil are rooted in one and the same being - soon brought him into conflict with Lutheran orthodoxy. It is in 'The Signature of all Things' (Signatura Rerum) that the tenets of Boehme's theosophy are related in their greatest detail. Casting the reader into the vortex of his cosmological universe, Boehme's endeavour to express a new sense of the human, divine and natural realms attains its apotheosis in his conception of the Ungrund, the uncertainty that precedes the divine will's arousing itself to self-awareness. Challenging and rewarding in equal measure, this is a profound text, deeply influential upon devotional writers such as William Law, visionaries such as William Blake (informing The Marriage of Heaven and Hell) and, more recently, upon cultural production as diverse as the psychology of Carl Jung and Philip Pullman's His Dark Materials trilogy.

This devotional classic, written by William Law, an eloquent religious teacher of the eighteenth century, was designed to prod indifferent Christians into making an honest effort to live up to what they professed to believe. It has been appreciated in every succeeding generation because of its innate vigor and virility.