There are two classes of human beings, namely the atheist and the devotee of the Lord. Similarly, there are two types of demons - the material, and the transcendental. The atheists are the material demons, while the transcendental demons are actually advanced devotees that incarnate along with the Lord in order to act out various pastimes. The Lord never involves the materialistic demons in his transcendental pastimes, but engages only with the devotees.
The devotee of the Lord, because of manifesting godly qualities, is called a demigod, whereas the atheist is called a demon. The demigods concern themselves with the spiritual upliftment of human society, whereas the demons are concerned with physical and material upliftment. Demons manufacture their own gods, or they claim to be God.
Since the beginning of creation, the demons and the demigods, or the Vaisnavas, are always the two classes of living beings to dominate the planets of the universes. Lord Brahma is the first demigod, and Hiranyaksa is the first demon in this universe. When natural disturbances occur on a planet, one should understand that a demon must have taken birth there. In the present age the number of demoniac people is increasing; therefore natural disturbances are also increasing.
The demons cannot stand the presence of Visnu, the Personality of Godhead, and are always busy in trying to vanquish the Personality of Godhead. But as soon as the Personality of Godhead appears, by either His transcendental name, form, attributes, pastimes, paraphernalia or variegatedness, the demon is at once vanquished. It is said that a ghost cannot remain as soon as the holy name of the Lord is chanted. The great saints and devotees of the Lord are in the list of His paraphernalia, and thus as soon as a saintly devotee is present, the ghostly sins are at once vanquished. That is the verdict of all Vedic literatures. One is recommended, therefore, to associate only with saintly devotees so that worldly demons and ghosts cannot exert their sinister influence.
Divine and Demoniac Natures
"Arrogance, pride, anger, conceit, harshness and ignorance--these qualities belong to those of demoniac nature, O son of Prtha."
"In this verse, the royal road to hell is described. The demoniac want to make a show of religion and advancement in spiritual science, although they do not follow the principles. They are always arrogant and proud in possessing some type of education or so much wealth. They desire to be worshiped by others, and demand respectability, although they do not command respect. Over trifles they become very angry and speak harshly, not gently. They do not know what should be done and what should not be done. They do everything whimsically, according to their own desire, and they do not recognize any authority. These demoniac qualities are taken on by them from the beginning of their bodies in the wombs of their mothers, and as they grow they manifest all these inauspicious qualities."
Bhagavad-gita 16-4 Text and Purport
"The conditioned living entities are divided into two classes in this world. Those who are born with divine qualities follow a regulated life; that is to say they abide by the injunctions in scriptures and by the authorities. One should perform duties in the light of authoritative scripture. This mentality is called divine. One who does not follow the regulative principles as they are laid down in the scriptures and who acts according to his whims is called demoniac or asuric. There is no other criterion but obedience to the regulative principles of scriptures. It is mentioned in Vedic literature that both the demigods and the demons are born of the Prajapati; the only difference is that one class obeys the Vedic injunctions and the other does not."
Bhagavad-gita 16-6 Purport
Krsna's Pastimes with the Demons
Lord Krsna descended in Vrindaban to mitigate the suffering on the earth. In order to enjoy those pastimes, the Lord ordered all the denizens of the heavenly planets to take birth in Vrndavana in different families of the Yadu and Vrsni dynasties. These personalities descended from the heavenly planets to see the pastimes of the Lord, which consist of saving the devotees and killing the demons.
In order to demonstrate these activities, the Lord called for devotees from different parts of the universe. The members of the Yadu and Vrsni dynasties and the inhabitants of Vrndavana were demigods or almost as good as demigods. Even those who externally helped the activities of the demons belonged to the higher planetary systems. The Lord came to play the part of a demon-killer, and a friend, son and brother to His devotees, and thus these devotees were all summoned.
The Supreme Personality of Godhead has all the tendencies that may be found in the living entity, for He is the chief living entity. Therefore it is natural that sometimes Lord Visnu wants to fight. Just as He has the tendencies to create, to enjoy, to be a friend, to accept a mother and father, and so on, He also has the tendency to fight. Sometimes important landlords and kings keep wrestlers with whom they practice mock fighting, and Visnu makes similar arrangements. The demons who fight with the Supreme Personality of Godhead in the material world are sometimes His associates. When there is a scarcity of demons and the Lord wants to fight, He instigates some of His associates of Vaikuntha to come and play as demons.
There have been many historical incidents in which the Lord killed a demon, but the demon attained a higher position by the mercy of the Lord. Putana is an example. Putana's purpose was to kill Krsna. She approached the house of Nanda Maharaja with the purpose of killing Krsna by smearing poison on her breast, yet when she was killed she attained the highest position, achieving the status of Krsna's mother. Krsna is so kind and impartial that because he sucked Putana's breast, He immediately accepted her as His mother. This superfluous activity of killing Putana did not diminish the Lord's impartiality. He is the friend of everyone. Therefore partiality cannot apply to the character of the Supreme Personality of Godhead, who always maintains His position as the supreme controller. The Lord killed Putana as an enemy, but because of His being the supreme controller, she attained an exalted position as His mother. Ordinarily a murderer is hanged, and in the Manu-samhita it is said that a king bestows mercy upon a murderer by killing him, thus saving him from various kinds of suffering. Because of his sinful activities, such a murderer is killed by the mercy of the king. Krsna, the supreme judge, deals with matters in a similar way because He is the supreme controller. The conclusion, therefore, is that the Lord is always impartial and always very kind to all living entities.
Being killed by the Personality of Godhead is a great fortune. Since the Lord is absolute, His acts of violence and nonviolence are both on the absolute platform. There is no difference in such acts of the Lord. Mundane violence and nonviolence have nothing to do with the Lord's acts. A demon killed by Him attains the same result as one who attains liberation after many, many births of penance and austerity. When the Supreme Personality of Godhead becomes angry or kills a demon, materially this may appear unfavorable, but spiritually it is a blissful blessing upon him. Therefore pure devotees do not make any distinction between the Lord's anger and His blessings. They see both with reference to the Lord's behavior with others and themselves. A devotee does not find fault with the behavior of the Lord in any circumstances. When a demon continuously thinks of Krsna because of enmity toward Him, he is certainly freed from the sinful reactions of his life. To think of Krsna in any way, in terms of His name, form, qualities, paraphernalia or anything pertaining to Him, is beneficial for everyone.
Bhaktivedanta Book Trust. Excerpted from various texts and purports of HDG A.C. Bhaktivedanta Swami Srila Prabhupada.