While etymologically blasphemy may denote the derogation of the honor due to a creature as well as of that belonging to God, in its strict acceptation it is used only in the latter sense. Hence it has been defined by Francisco Suárez as "any word of malediction, reproach, or contumely pronounced against God. It is to be noted that according to the definition (1) blasphemy is set down as a word, for ordinarily it is expressed in speech, though it may be committed in thought or in act. Being primarily a sin of the tongue, it will be seen to be opposed directly to the religious act of praising God. (2) It is said to be against God, though this may be only mediately, as when the word is spoken of the saints or of sacred things, because of the relationship they sustain to God and His service.
Blasphemy, by reason of the significance of the words with which it is expressed, may be of three kinds.
It is heretical when the insult to God involves a declaration that is against faith, as in the assertion: “God is cruel and unjust” or “The noblest work of man is God”.
It is imprecatory when it would cry a malediction upon the Supreme Being as when one would say: “Away with God”.
It is simply contumacious when it is wholly made up of contempt of, or indignation towards, God, as in the blasphemy of Julian the Apostate: “Thou has conquered, O Galilaean”.
Again, blasphemy may be (1) either direct, as when the one blaspheming formally intends to dishonor the Divinity, or (2) indirect, as when without such intention blasphemous words are used with advertence to their import.