The four ancient yoga pathways to spiritual union taught in the Bhagavad Gita are built on the profound recognition, made by yoga masters thousands of years ago, that human beings have four faculties through which they can learn to purify the heart, discipline the mind, restrain the senses, and unite with the Self within: the intellect, love, psychic control, and work. Swami Vivekananda describes the four yogas as such:

“Each soul is potentially divine, and the goal of yoga is
 to manifest this Divinity within
 by controlling nature, external and internal.