Islam and Christianity; or should it be, Islam and Christendom? In the difference between the connotation of the words Christianity and Christendom lies the explanation of one of the most essential differences between the two faiths. For Islam is a way of life, and perhaps, in selecting ‘Christendom’ in preference to ‘Christianity’ in the context of comparing the two religions, the tendency is evinced to seek a term referring to Christianity as if it, too, were a way of life in the same, all-embracing way that Islam set out to be. But Christianity is a religion; in some respects an institution that happens in spite of terrestrial life, although a life which it does not inform is death. Christendom remains a territorial concept, so that, though it does in a sense express an antithesis which the existence of Islam called into being, it cannot be used to mean what Islam meant-to refer to the way men worshipped, wrote, thought, practised the law, washed themselves, devised systems of finance that would not break the law and so forth. Christendom was a place; Islam a complete and monolithic concept of human conduct.
Christianity was never a way of life to the same degree because, for one thing, its founder, Jesus Christ, had not been at pains to legislate for this world, only to save it by symbolical and actual death to it. He had preached its unworthiness and left no doubt that what is God's is what counts, not what is Caesar's.