'The eye through which I see God is the same eye through which God sees me; my eye and God's eye are one eye, one seeing, one knowing, one love' – Meister Eckhart

'To see a World in a Grain of Sand | And a Heaven in a Wild Flower, | Hold Infinity in the palm of your hand | And Eternity in an hour' – William Blake (1757-1827 

Troughout the ages people of all faiths have had mystical experiences. Mysticism (the Greek word from which it is derived literally means ‘I conceal’, the related ‘mystikos’  means ‘initiate’) is the attempt to achieve a personal union of the soul with God. In a non-religious, wider sense, the term is also used to indicate a state of consciousness beyond human perception or a feeling of being one with nature or creation.

The BPH mainly collects works by Western mystics, ranging from the great medievals Meister Eckhart, Tauler, Suso and Hildegard von Bingen to the later Protestant mystics, foremost among whom is the German shoemaker-theosopher Jacob Böhme. Works by ‘spiritualists’ are another primary focus of this collecting area. The spiritualists also held that direct contact of the soul with the supreme being was essential and therefore rejected any mediators between the two (the established churches, dogmas, sacraments, spiritual officials) or at least wished to relegate them to a subordinate role. The term ‘spiritualists’ is primarily used for sixteenth-century thinkers such as Caspar von Schwenckfeld and Sebastian Franck, who set great store by direct inspiration through the Spirit rather than adherence to the literal text of the Bible. Important spiritualists in the Netherlands were the self-proclaimed prophets David Joris and Hiel (Hendrik Jansen van Barrefelt).

The spiritualists made a sharp distinction between ‘the flesh’  and ‘the spirit’. The world of the flesh was the domain of visible, concrete things such as church ceremonies, secular authorities, but also the literal text of the Bible.  It was necessary to relinquish the things of the flesh to become a spiritual creature. Anyone who continued to follow the letter of the Bible , therefore, stayed a ‘man of the flesh’ . Only a ‘man of the spirit’  was able to grasp the innermost meaning of the Word. Most spiritualists were ridiculed and even persecuted because of their unorthodox beliefs: a number of them even died at the stake.

After the Reformation (1517) the legacies of Luther and Calvin were codified in theological rules and dogmas by the established churches. Various philosophical and religious thinkers, (radical) reformers and spiritualists strove for freedom of religion and against the Orhtodox religion, whether Catholic or Protestant. The largest group of religious dissenters in the second half of the 17th century were Protestant Pietists, who aspired to personal piety and a simple Christian life. The 17th-century Republic, specifically Amsterdam, was the place where many works by these religious and other radical thinkers, who were banned in their native countries, could be printed.