On 8 September 1907, Pope St. Pius X promulgated the encyclical “Pascendi Dominici Gregis” to expose and oppose the troubling spread of Modernist errors within the Church. He identified Modernism, which he termed the “synthesis of all heresies," as a significant threat to the faith, originating from both outside and inside the Church. Alarmingly, it was not just lay members who were drawn to these modern ideas; several clergy members, including priests, were also embracing these errors. Under the impression that they were aiding the Church's development, they were actually undermining and corrupting her doctrines.
This “Catechism on Modernism” by Fr. J. B. Lemius, written in a question-and-answer format, helps to clarify the complex issues surrounding Modernism. This approach is particularly beneficial for those unfamiliar with the evolution of doctrines, true or false. It also aids those susceptible to errors often masked under the guise of scientific advancement, assisting them in recognizing the true nature of these modern errors.
This book also serves as a wake-up call for Catholics today, reminding them of the persistent threat of Modernism and its capacity to distort the Church’s teachings. By shedding light on the dangers of Modernist thought, the book urges the faithful to adhere firmly to the authentic teachings of the Church, even when the world tries to convince us otherwise with ideas that sound good but are actually harmful.