In the Bhagavad-gītā (6.47) Lord Kṛṣṇa says,
And of all yogīs, the one with great faith who always abides in Me, thinks of Me within himself, and renders transcendental loving service to Me—he is the most intimately united with Me in yoga and is the highest of all. That is My opinion.
The fruitive workers cannot be counted among the yogīs. The actual yogīs are the karma-yogīs, the jñāna-yogīs, the aṣṭāṅga-yogīs, and the bhakti-yogīs. Factually they are the same, although named differently. The yogic process is like a ladder one ascends gradually toward the final goal of the Absolute Truth. Niṣkāma-karma, or renunciation of the fruits of one's labor, is the first step on this ladder. When knowledge and austerity are added to it, it becomes jñāna-yoga, the second step in this ladder. And when meditation on the Supreme is added to jñāna-yoga, the third step is reached, namely aṣṭāṅga-yoga. Finally, when loving devotional service to the Supreme Lord is practiced along with aṣṭāṅga-yoga, it is transformed into bhakti-yoga. This entire successive process is yoga. For an exact and clear delineation of the subject of yoga, all four steps need to be explained separately. Those who desire the best for humanity take to the path of yoga. The process for progressing in yoga requires, first, determination and strict execution of discipline at each stage. When a person is firmly situated at one stage, he then has to relinquish attachment and adherence to the practices of that stage in order to elevate himself to the next higher stage. Those who cannot reach the top for some reason and get stuck at any one of the four stages acquire the designation of that particular stage. Thus there are karma-yogīs, jñāna-yogīs, aṣṭāṅga-yogīs, and bhakta-yogīs. Lord Kṛṣṇa instructs Arjuna that one who renders loving devotional service to Him, the Supreme Lord, is the highest among all yogīs, and that Arjuna should thus strive to become such a bhakti-yogī.
The successive, step-by-step spiritual path is not the same as step-by-step progress in the material world. In the mundane process the rules of progress are strict and cannot be transgressed. If one wants to acquire a doctorate at a university, he has to begin from the elementary school level and gradually work upwards. It is impossible to go directly to the university without prior schooling. In spiritual life, however, although there are strict regulations, by the Supreme Lord's grace one can bypass many intermediary stages and reach the top, or "doctorate" level. One can attain this divine grace by intimate and constant association with the Supreme Lord. And such intimate association with the Lord comes about through confidential exchanges with a pure devotee of the Supreme Lord. Everyone of us is intimately and eternally related to the Supreme Lord, but due to the bad influence of māyā we have forgotten our relationship with Him.
The living entities are like sons of the Lord, and as such they are rightful heirs to the great wealth of their rich father. But because of the reactions to sins committed in previous lives, they are roaming about without a home, suffering acute poverty. That the living entities are suffering is quite clear to all. But they do not know who their wealthy father is or where they can go to reclaim their valuable inheritance. Without proper knowledge, they are trying in vain to escape from their poverty while aimlessly roaming about like poor beggars. They meet many who promise to help them, but in the end such helpers turn out to be beggars themselves. A few among these strangers seem rich and prosperous, but the directions they give do not lead to the father's house, and so the living entities' poverty knows no end. The wealthy strangers suggest many paths, such as karma, jñāna, or dhyāna, but the problem of poverty remains unsolved. The living entities can escape their poverty only by learning and practicing the science of devotional service to the Supreme Lord. Caitanya Mahāprabhu, the Supreme Personality of Godhead and the source of all incarnations, explained the science of devotional service to Śrīla Rūpa Gosvāmī at Prayāga (Allahabad). These instructions are the crest jewel of teachings for all humanity. In Śrī Caitanya-caritāmṛta (CC Madhya 19.151), the Lord says,
According to their karma, all living entities are wandering throughout the entire universe. Some of them are being elevated to the upper planetary systems, and some are going down to the lower planetary systems. Out of many millions of wandering living entities, one who is very fortunate gets an opportunity to associate with a bona fide spiritual master by the grace of Lord Kṛṣṇa. By the mercy of both Lord Kṛṣṇa and the spiritual master, such a person receives the seed of the creeper of devotional service.
By the mercy of Lord Kṛṣṇa, this seed of devotion is available in the Bhagavad-gītā. Only one who is able to receive this devotional seed can understand the purport of the Bhagavad-gītā. Otherwise, simply repeatedly reading the Bhagavad-gītā and discussing its teachings will not produce any results.
In the Bhagavad-gītā, Lord Kṛṣṇa Himself reveals the truth about Himself. When an ordinary mortal writes an autobiography, he receives many accolades, but when the Supreme Lord writes about Himself, we unfortunately do not fully believe in His words. Furthermore, we overlook the cardinal issues in His writings and quibble over lesser subjects, trying to magnify them by giving them concocted connotations and meanings. This practice is stretched to such absurdity that the original meaning is lost and the lop-sided conclusions attract only ridicule from readers. In the Bhagavad-gītā Lord Kṛṣṇa unequivocally declares that He is the Supreme Absolute Truth and that it is the duty of everyone to render Him loving devotional service. The Bhagavad-gītā was revealed for the sole purpose of explaining these two principal points. One who understands them is eligible to begin spiritual life as a neophyte devotee. Śraddhā, or faith, is the first prerequisite in spiritual life and is described as synonymous with neophyte devotion. Thus Śrī Caitanya-caritāmṛta (CC Madhya 22.62) says,
By rendering transcendental loving service to Kṛṣṇa, one automatically performs all subsidiary activities. This confident, firm faith, favorable to the discharge of devotional service, is called śraddhā.