jmherbenerThe context of Lecture 5, slide 4 is a person has different consumer goods, of which the units of each can be put to different ends. The units of each good exhibit diminishing marginal utility as a person allocate them to the highest-valued ends first (logically) and then to progressively less-valuable ends. In choosing between using one of the goods, say X, rather than the other, say Y, the person will choose to act with the good that has the highest MU (for using the 1st unit), say X. But since using more of X lowers its MU (for using the 2nd unit, and so on), acting with Y would be chosen when its MU (for using its 1st unit) exceed the MU of X for the not yet chosen unit (say the 4th unit). The greatest utility in allocating the two goods, then, comes by using their units in such a way that their MUs do not differ significantly. Otherwise, the person could reallocate units away from the lower MU unit of one good and toward the higher MU unit of the other good.
Leisure is a good and therefore subject to the same analysis. So, yes we are always engaged in action as long as we have unmet ends. But the logical requisite of explaining what particular acts of consumption a person is engaged in is differences in the MU of the units of different goods. This is what the slide is referring to when it says, “action is renewed by changes in underlying factors that regenerate differences in MUs.” It’s not a reference to action per se, but to particular acts of consumption.
Of course, consumption is only one subcategory of action. Production and trade are other subcategories. So, a person would also be choosing across acts of consumption, acts of production, and acts of trade.