Kant’s most important work on the philosophy of religion in which he makes the case that religion can be entirely placed within reason rather than revelation.
The book consists of four ‘Pieces’, originally written as a series of four journal articles, in which Kant attempted “to develop the parallels between revealed religion and philosophical theology. In true Enlightenment fashion he claimed that all that is essential in religion can be reduced to morality, but he does not reject the main tenets of traditional religion. They are valuable, if only we realise that they are not knowledge, but ‘nothing more than two articles of belief’, namely the belief in God and the belief in immortality” (Kuehn, p. 250).
The collection of essays does not merely amount to ‘a theoretical treatise, meant as a contribution to the philosophy of religion; it was also a political act [and] Kant’s declaration of loyalty to Lessing and Mendelssohn. Kant’s Religion, Lessing’s Education of the Human Race (1780), and Mendelssohn’s Jerusalem (1783) were all valiant attempts to introduce into Prussia the kind of religious freedom that had by then already been achieved in the United States. Lessing and Mendelssohn were dead. Kant carried on the fight. That he was concerned not only with religious freedom but ultimately with full-fledged civil freedom, is clear’ (Manfred Kuehn, Kant: A Biography, pp. 371-2). However, it ultimately brought Kant the disfavour of King Frederick Wilhelm II of Prussia due to its non-conformist ideas, leading to the suppression of Kant’s works and forcing him to cease lecturing philosophy until after the Kings death in 1797.
Warda, 141.