The conditioned life of a living being is caused by his revolting against the Lord. There are men called deva, or godly living beings, and there are men called asuras, or demons, who are against the authority of the Supreme Lord. In the Bhagavad-gītā (BG Sixteenth Chapter) a vivid description of the asuras is given in which it is said that the asuras are put into lower and lower states of ignorance life after life and so sink to the lower animal forms and have no information of the Absolute Truth, the Personality of Godhead.
-Shrimad Bhagvatam Canto 1 Chapter 2 Verse 16, Translation and Purport

वासुदेवे भगवति भक्तियोग: प्रयोजित: ।
जनयत्याशु वैराग्यं ज्ञानं च यदहैतुकम् ॥ ७ ॥
By rendering devotional service unto the Personality of Godhead, Śrī Kṛṣṇa, one immediately acquires causeless knowledge and detachment from the world.
-SB 1.2.7