Just for giggles...
Assuming you've time, compare Heinlein's Moral Philosophy to Maslow's Hierarchy of Needs. Note how the criticisms of Maslow from Max-Neef and from Hofstede apply to Heinlein's work as well. (Fair notice: all three are psych, not philosophy. But I think they're an easier row to hoe than Kant or Hume and their Duties and Responsibilities.)