The prophet married social outcasts such as widows [they were out casted during this era] , because they experienced hardships in their lives [because of their social status]. One thing to remember is how society was back then, how how it is now. For instance, they didn't even have doors back then, it was like the flinstones [houses made out of stone]. Just to give you an image = ) Why is it permissible to have upto four wives? First off, No man is allowed to marry upto four wives because of sexual gratification. We follow the practices of Prophet Muhammad [PBUH] and this is why we marry upto four wives. - The prophet would marry unfortunate women. Widows were social outcasts and shunned upon during quranic/biblical times. No one married the widows and they suffered great depression, because of their social status. These women were heckled and shunned upon in the face of society. So the prophet mostly married widows (who were older than him even), something which was unheard practically, during this time. EX. The prophets first wife was KHADIJAH, she was a widow. She remained the only wife of the prophet for the next twenty-five years, until she died (may Allah be pleased with her). SAWDA BINT ZAM'A was a wife of the prophet. She was 65 years old, poor, and had no one to care for her. This was why Prophet Muhammad (pbuh) married her. Etc. One must have an understanding of the old customs of Arabia in order to truly appreciate the prophets intentions. By marrying these women, he took a great burden off them, and gave them affection. Now lets compare this to modern society or other society's that aren't so 'modern' There are plenty of other instances where men can marry other unfortunate women as the prophet did, this is called sunna in arabic. Since modern society doesn't really have a need for polygamy (Since widows can easily remarry in most societies now, without any problems), many muslim countries don't practice polygamy. Rarely will you ever find a man with more than one wife in most muslim countries. As a matter of fact, polygamy is banned in muslim Tunisia, Turkey and Lebanon. Polygamy, and laws concerning polygamy, differ greatly throughout the Islamic world and form a very complex, and diverse background from nation to nation. Whereas in a few Muslim countries it may be fairly common, in most others it is often rare or non-existent. According to traditional Islamic law, a man may take up to four wives. Polygamy is traditionally restricted to men who can manage things, and in some countries it is illegal for a man to marry multiple wives if he is unable to afford to take care of each of them properly. In the modern Islamic world, polygamy is mainly found in traditionalist Arab cultures, Saudi Arabia and the United Arab Emirates for instance, whereas in secular Arab states like Lebanon and non-Arab countries with Muslim population, Turkey for example, it is banned. It is also illegal in Tunisia. I would also like to point out that there are a significantly larger amount of females in comparison to males in countries such as the United Stated Of America (and this is growing). These females will not have partners, because of the shortage of the male population. So wouldn't polygamy make sense in this instance as well?