The Doctrine and Practice of Yoga: Including the Practices and Exercises of Concentration, both Objective and Subjective, and Active and Passive Mentation, an Elucidation of Maya, Guru Worship, and the Worship of the Terrible, also the Mystery of Will-Force

"The Doctrine and Practice of Yoga" by Swámi A. P. Mukerji is a philosophical guide on yoga and self-development written in the early 20th century. The text provides practical instructions on various aspects of yoga, concentration techniques, and the spiritual evolution of the individual, emphasizing the importance of the inner journey towards self-realization and understanding. At the start of the work, the author addresses students embarking on their study of yoga, emphasizing three key points: the conciseness and depth of the material, the need for patience in spiritual training, and the interconnectedness of these lessons with other related spiritual texts. The opening discusses the essential concept of concentration, contrasting objective concentration (focused on external goals and worldly achievements) with subjective concentration (turning the mind inward towards spiritual enlightenment). The author posits that true power and insight come from introspection, defining these two forms of concentration as critical in understanding spiritual principles and achieving mastery over one's mind. This section sets the stage for further exploration of techniques and practices that promote both mental and spiritual strength.