Fire is conserved in wooden sticks, and when circumstances are favorable, the fire is ignited. But the wooden sticks which are the cause of the fire are also consumed by the fire if it is properly dealt with. Similarly, the living entity's conditional life of material existence is due to his desire to lord it over material nature and due to his envy of the Supreme Lord. Thus his main diseases are that he wants to be one with the Supreme Lord or he wants to become the lord of material nature. The karmīs try to utilize the resources of material nature and thus become its lord and enjoy sense gratification, and the jñānīs, the salvationists, who have become frustrated in enjoying the material resources, want to become one with the Supreme Personality of Godhead or merge into the impersonal effulgence. These two diseases are due to material contamination. Material contamination can be consumed by devotional service because in devotional service these two diseases, namely the desire to lord it over material nature and the desire to become one with the Supreme Lord, are absent. Therefore the cause of material existence is at once consumed by the careful discharge of devotional service in Kṛṣṇa consciousness.
A devotee in full Kṛṣṇa consciousness appears superficially to be a great karmī, always working, but the inner significance of the devotee's activities is that they are meant for the satisfaction of the Supreme Lord. This is called bhakti, or devotional service. Arjuna was apparently a fighter but when by his fighting he satisfied the senses of Lord Kṛṣṇa, he became a devotee. Since a devotee also engages in philosophical research to understand the Supreme Person as He is, his activities may thus appear to be like those of a mental speculator, but actually he is trying to understand the spiritual nature and transcendental activities. Thus although the tendency for philosophical speculation exists, the material effects of fruitive activities and empiric speculation do not, because this activity is meant for the Supreme Personality of Godhead.