Giving human advice on sex from the standpoint of Christian Science is like steering between Scylla and Charybdis. If we encourage sexual relationships at all, we appear to be approving of pleasure in matter. But if we say that sex is evil, we appear to be agreeing that we are all conceived in sin — a doctrine Christian Science refutes.
Perhaps we wish we could work out a complete set of rules — a code of conduct. But there would always be the situation the compilers of the code hadn't thought of. What's more, there would be the danger of the reverse effect — the rules suggesting things to do that the boys and girls hadn't thought of.
Then there is the hypocrisy problem. Rules tend to turn attention away from inward motives to outward acts. Christ Jesus made quite a point of this. He denounced those who went through the motions of prayer with no prayer in their hearts. He ridiculed those who made a show of giving alms with no charity in their hearts. And of sexual behavior he said: "Ye have heard that it was said by them of old time, Thou shalt not commit adultery: but I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart." Matt. 5:27, 28;