You're probably familiar with chivalry, the amorphous set of behavior guidelines for the aristocratic male warrior class of later medieval Europe that constructed ideals of "nobility" and "honour." You're probably also familiar with the reality on the ground, in which chivalrous warfare meant sure, you'll just take the richest nobles hostage for ransom, but mow down the rest of the opposing force after your victory. Although an important point of chivalry was its limited applicability to the upper class, it's a useful guide for showing two key features of basic medieval European morality: first, medieval European discourse LOVED guidelines for proper behavior. Second, their application in real life depended heavily on how a person or community defined "us" and "them."
The primary lens for moral instruction was Christianity, and from the twelfth and especially thirteenth centuries, a primary focus of pastoral Christianity was moral instruction. Until the very end of the Middle Ages, the primary framework for teaching morality was the seven deadly sins. (In the fifteenth century, the Ten Commandments rise to prominence and then preeminence). Now, it's important to remember that religious practice here is ultimately eschatological, that is, aimed towards God and salvation after death. The seven deadly sins are ultimately sins that separate the sinner from God. However, while you can dispute the effectiveness of some of the ideas, preachers and authors of didactic literature absolutely got into the daily life grit of some basic issues--and the usefulness of a moral code based on motives as well as actions.
The most prominent and pressing from a human decency standpoint was ira, the sin of wrath. And over and over, the basic points stressed here are: don't commit homicide or arson. This is true in Church synods that condemn marauding nobles in the 11th century; it's true in pamphlets that fifteenth century mothers read to their children. "Don't murder" might seem like a low, if necessary, bar, but more is going on here. Wrath is more than specific actions: it can also be a motive for actions that may even look "good" on the surface. The greatest medieval virtue, moderation, is called into play here. It is okay to act "mean" as long as you are not doing so excessively or out of control.
A sad example here is domestic violence and child abuse. Medieval Europeans believed in correction through physical chastisement--definitely the stick. Husbands were encouraged to beat their wives, just not too hard; parents their children, just not too hard; and the stories of teacher-student violence are legendary. The point here was that the beater needed to have the best interests of the other person in mind: their ability to memorize Latin declension or to be properly obedient in domestic affairs. And yes, there are absolutely cases where "going too far" was a crime worth a criminal conviction or permission for a husband and wife to live apart. Surely not often enough, but the idea was present and important.
Other sins operated on a similar acts/motives principle in the formulation of guides for behavior. I'd like to move onto a positive (in the sense of encouraging behavior rather than discouraging) teaching now: charity. Caritas is the Latin term for, essentially, "brotherly love." In later medieval Christian society, it began to take on specific connotations of the longstanding Christian mission to help the weak and needy: widows, orphans, immigrants. It also came to mean helping the suffering Church, that is, Christians in purgatory. The Church was the primary funder and organizer of social charity, but of course it depended on people's tithes. Prayers and paying for candles/Masses for the dead was also a bedrock practice.
Of course, the richer someone was, the greater their responsibility to the poor. It became a standard practice for the funerals of urban elites to distribute massive amounts of money to indigent Christians in attendance. In some cases, the deceased would also arrange more concrete benefits, such as the Londoner who paid for thousands of beggars to receive new clothes in dark, mourning colors. (The side benefit, if you will, was receiving the prayers of all the beggars there to speed the rich man through purgatory).
Were there social obligations to "help people out", especially strangers? Yes, there is ample evidence for that. Actually, one example came up recently in a thread on speed limits in medieval streets. An angry English squire had galloped so fast through London streets that he knocked over a woman carrying a child. A bystander, no relation, promptly took him to task for his reckless action.
A more systemic idea is what scholars call the "moral economy": that is, the idea that everyone ("everyone") has a basic right to food and shelter. In England, the price of a loaf of bread was fixed, so that even the destitute could always afford SOME bread. The size of the bread, however, would vary according to wheat prices. Food sellers who committed fraud, selling bad food or not actually food, were prosecuted as criminals, too.
But "basic human decency" also needs to have some limitations, and there were two very important factors in the Middle Ages. First, the line between commendable and excessive selflessness/charity. The later Middle Ages witnessed the rise of "living saints," holy women and some men renowned in their communities for their lives of piety, feats of asceticism, and spiritual gifts (revelations, levitation, etc). Even the strongest supporters of these aspiring saints are very clear: this is not a life for everyone. Catherine of Siena can volunteer at the leper hospital and even drink the pus squeezed from their wounds as a self-effacing "Eucharist", but maybe you should say some extra Hail Marys and fast more rigorously on Fridays. Or the flagellants, lay people and some clerics who believed heroic public self-injury would save humanity from God's looming wrath. To them, an act of charity, of basic human need. To the institutional Church, a threat to social order and basic moral praxis.
The second factor is, who counts. The development of chivalry is intertwined with the Crusades, so already there are the obvious fault lines of religion. They were never absolute--Jewish and Christian women in the Rhineland, for example, swapped clothing and breastfeeding duties with their friends across religious lines. Kind of the way Jewish doctors in America work Christmas and Christian ones work Yom Kippur. But the Middle Ages also nurtured the idea of the "deserving poor", that is, people whose poverty is perceived as "not their fault." Again, this is necessarily contingent on a situation and an individual's perspective. How "disabled" must someone be before their inability to secure steady work is judged legitimate? For all the attempts to legislate based on clear categories like "widows and orphans," the boundaries could never be clear in practice.
A final case of "who counts" that I'll mention here encompasses a lot of the other issues we've looked at, including the distance between prescription and practice. In medieval warfare around the Mediterranean, loot was the victorious soldiers' right: loot in goods, and loot in human massacre, rape, and chattel. And the scraps that we see in Christian writing before scholars turn to debating laws of war in the 14C are pretty clear: this is absolutely unconscionable when the other side does it. They are horrible evil animals. Defining what the "barbarian other" stereotypically does is, perhaps, the ultimate method of communicating a society's values of humanity and civilization.
So, uh, the Europeans write, nothing to see here.