In this thesis our daily held beliefs about what would be an (un)reasonable moral demand are discussed. In a philosophical context, our commonsense beliefs about the limits that we should respect to the obligations and duties that can be imposed on moral agents, are not easily defended, even though they are widely held by many. My thesis is that these commonsense ideas have not been done justice so far in the philosophical debate, and I therefore concentrate on an analysis of the content of our ideas about reasonable demands, which I formulate as a Reasonableness Claim. I argue that the belief that some burdens will be unreasonable from an agent's perspective is at least supported in four different ways by commonsense morality. This makes i...