An excerpt from Stanford Encyclopedia of Philosophy's entry on morality that matches fairly well today's class discussion:
On all accounts of morality, it is a code of conduct. However, on ethical or group relativist accounts or on individualistic accounts, apart from avoiding and preventing harm, morality has no special content or features that distinguishes it from nonmoral codes of conduct, such as law or religion. Just as a legal code of conduct can have almost any content, as long as it is capable of guiding behavior, and a religious code of conduct has no limits on content, all of the relativist and individualist accounts of morality, have almost no limit on the content of a moral code. However, for those such as Hobbes, (Leviathan and De Cive) who hold that morality is a code of conduct that all rational persons would put forward for governing the behavior of all moral agents, it has a fairly definite content. Kant, in accordance with the German word “moral” that is used to translate the English word “morality,” regards morality as applying to behavior that affects no one but the agent, but most of the behavior that he discusses is behavior that affects other people. Hobbes, Bentham, Mill, and most other non-religiously influenced philosophers writing in English limit morality to behavior that, directly or indirectly, affects others.
The differences in content among those philosophers who use “morality” to refer to a universal guide that all rational persons would put forward for governing the behavior of all moral agents are less significant than their similarities. For all of these philosophers, such as Kurt Baier, Philippa Foot, and Geoffrey Warnock, morality prohibits actions such as killing, causing pain, deceiving, and breaking promises. For some, morality also requires charitable actions, but it does not require a justification for not being charitable on every possible occasion in the same way that it requires a justification for any act of killing, causing pain, deceiving, and breaking promises. Both Kant and Mill mark this distinction by talking of duties of perfect obligation and duties of imperfect obligation. For others, morality only encourages charitable actions, and no justification is ever needed for not being charitable. Rather, being charitable is encouraged but not required; it is always morally good to be charitable, but it is not immoral not to be charitable.