(1) If one does not believe in Allah at all or refuses to accept Him as the Supreme Authority or as one's Master and that of the entire Universe or as the only God of worship, or

(2) If one professes to acknowledge Allah but refuses to accept His commandments and Guidance as the sole source of the knowledge of Truth and of Law, or

(3) If one accepts on principle the Guidance of Allah, but refuses to accept the authority of the Messengers whom Allah has sent with His Commandments and Guidance, or

4) If one accepts a particular Messenger (or Messengers) and rejects others according to one's whim or prejudices, or

(5) If one discards the whole or any part of the Islamic creed, or its code of life, or the teachings of the Messenger, or

(6) If one accepts all these things in theory but discards the Commandments of God deliberately in practice and persists in this conduct and leads a life of rebellion instead of submission.

All the above modes of thought and action are rebellion against Allah and are kufr according to the Qur'an. Besides the above usages, the Qur'an sometimes uses the word kufr in the sense of ingratitude as an antonym of shukr. Shukr means that one should be grateful only to Him Who has bestowed the blessing, should appreciate His favour,.should use and spend the blessing only according to His Will, and should submit to Him completely and faithfully like a loyal servant. On the contrary, kufr or ingratitude is that one should either refuse to acknowledge the favour of one's benefactor, and should regard it as a result of one's own ability, or as a favour and result of the influence of another one, or should depreciate the blessing bestowed by Him and waste it, or should use the blessing against His Will, or should adopt an attitude of rebellion against him inspite of His favours and blessings. Such an attitude of kufr is generally described as ingratitude, disloyalty, rebellion and treason.   "