Psak bean counting vs holistic

I recently received the following question

 It's been a discussion and I'm hoping you can point me to sources as to how singles should understand the actual halacha about :singles having sex

Singles going to mikva

There's all types of people throwing around their opinions and thoughts and feelings but some folks want to live as close to God as possible given the circumstances. They don't want to be above and beyond at this point. 

I appreciate it. 

I replied

 It is not a simple question and depends whether halacha is decided by the bean counting approach or the holistic approach

The standard approach for many years is that of Rav |Moshe

Igros Moshe (EH IV #60) Question:Is dating for social not marriage permitted?Answer Concerning the issue of a young man who is not ready to get married and has no interest in getting married and he is interested in having social dates with young women who also are not ready to get married and have no interest in getting married. They say that since they are careful to avoid the prohibition of yichud (seclusion) there is no prohibition in dating. Even though they know that this is not nice, they say they are not interested in issues of piety and extra measures of modesty and they don’t want to listen to lectures of mussar and rebuke. However they say that they will stop if they hear from me that this is prohibited according to the halacha. Therefore I am forced to respond immediately because this applies to a current activity… There is also a severe prohibition from the Torah in close friendships between a young man and woman. That is even if they avoid hugging and kissing as well as touching and yichud. The problem is that he talks with her for extended times in expressing love and he gets pleasure from this and stares at her. Even according to the Ramban who disagrees with the Rambam and holds this is only a rabbinic prohibition nevertheless agrees that this is a severe prohibition since it has an asmachta from a verse and that it is punished with rabbinic flogging. It is clear that dating is done because of the love of women and not because of ordinary friendship since he clearly prefers being with a woman then with male friends. Why is he interested in this woman when it doesn’t give him greater respect or a good name? It is obviously because of love of a woman because she is a woman. In addition even though she is unmarried, she is a nidah which is prohibited with the punishment of kares…

However others say that this approach is just producing intermarriage in present times.

Rav \yakov exemplifies the holistic approach

Rav Yaakov Kaminetsky(Emes LeYaakov Parshas Yechi page 237): A practical example of zealousness which is not based on a correct reading of the halacha is found in the following question. A person has the choice of marrying a Jewish woman who doesn’t observe the laws of family purity or a non‑Jewish woman. Which is preferable? A student who has not properly served an apprenticeship with an experienced posek will say that it is obvious that the person should choose to marry the non‑Jewish woman. That is because sexual relations with a nidah is punished by kares while sexual relations with a non-Jew is only a violation of a negative commandment of the Torah which is not punished by kares. The truth is not this way. Rambam (Hilchos Issurei Bi’ah 12:7-8) states that even though sexual relations with a non-Jewish maidservant is only a rabbinic prohibition he rules that, "This sin [of sexual relations with a non‑Jew] even though beis din does not impose the death penalty should not be viewed as minor because there is a loss associated with it. Contrary to all other sexual transgressions in which the son of the relationship is still his son in every respect and has the status of a Jew – even if the child is a mamzer – but the child from a non‑Jewish mother is not his son as it says in Devarim (7:4): For they will turn away your son from following Me.” That means that the son has been removed from following after G‑d. This activity causes him to attach himself to non‑Jews which G‑d has separated us from them so that we would follow after Him and thus he is rejecting G‑d. “ It is clear from this that the person should choose the relationship with the Jewish woman even though she doesn’t observe the laws of family purity.

The issue is whether this is a monogamous relationship and whether she becomes a zona. There is also the issue of common law marriage which was a dispute between Rav Moshe and Rav Yakov. There is also the issue of pilegesh vs marriage

In sum everyone will say it is prohibited but there are a wide variety of reasons why while others will say it is not so bad especially if the issue is a goy or zera l'vatala.