Other difficulties arose from various causes. The influences of the heathen world, from which most of the Corinthian Christians had come and to which their friends and neighbours belonged, were always with them, and the problems created by these relations were very numerous. Christianity had brought over and had even intensified the moral code of Judaism, and, especially in the relations of the sexes, this brought a strain upon the naturalistic impulses and lower standards of converts trained in a different system.
Again, there were law-suits in the ordinary courts, a natural result of the frictions and strains of an oriental trading community. To Paul this was abhorrent, and here too he urges a complete break with their past. With regard to the social customs of meals at which meat that had been offered in heathen sacrifices was a part, and of feasts actually at heathen temples, doubtful questions arose. Was it a denial of the faith to eat such food or not? Mixed marriages, too, had their problems; ought the believing wife to separate herself? Ought the believing husband to insist that his heathen wife stay with him against her will? And, further, in the case of slaves, does the consciousness of Christian manhood give a new motive for trying to gain worldly freedom? In all these matters Paul gives sensible advice. There were clearly two groups of Christians, the "weak," or scrupulous, whose principle was to abstain, and the "strong," or free, who maintained that the morally insignificant must not usurp a place to which it has no right. Paul sides with neither, but follows two principles, one that the church and its members must be kept pure, the other that the moral welfare not only of the individual but of his neighbour must be the controlling motive.
Not due so much to heathen influences as to the natural tendencies of imperfect and passionate human nature were other conditions. The most striking incident here, and one which gave Paul much concern, was the case of a man who after his father's death had married his own stepmother ("the case of incest"). That this was rare in the ancient world and generally abominated both by Jews and Greeks made it seem to Paul the more imperative that this stain on the Christian church should be removed. His language shows his indignation and grief that the Corinthians themselves have not already taken the matter in hand.