Those with whom she associated had gone through a similar training, and knew as little of life.
She had heard of "infidelity;" yes.

Live as long as she might, she would never forget one dreadful day when, in a quarrel with his mother, Reuben uttered words which signified hatred and rejection of all he had been taught to hold divine Mrs.Elgar's pallid, speechless horror; the severe chastisement inflicted on the lad by his father;--she could never look back on it all without sickness of heart.

Thenceforth, her brother and his wild ways embodied for her that awful thing, infidelity.

At the age which Cecily Doran had now attained, Miriam believed that there were only a few men living so unspeakably wicked as to repudiate Christianity; one or two of these, she had learnt from the pulpit, were "men of science," a term which to this day fell on her ears with sinister sound.
Thus prepared for the duties of wife, mother, and leader in society, she shone forth upon Bartles.

Her husband, essentially a coarse man, did his utmost, though unconsciously, to stimulate her pride and supply her with incentives to unworthy ambition.