Mengzi distinguishes between two sets of inclinations: physical ones (like our desire for tasty flavors) and moral ones (like the tendency of parents and children to interact with benevolent care). The moral inclinations are what Mengzi also calls our “sprouts”; you explored one of your sprouts in yesterday’s exercise.
Mengzi also distinguishes in this passage between an inclination’s being our “nature” and being “fated.” For Mengzi, “fate” refers to things outside our control. Our mouths are drawn toward sweetness more or less from birth; we do not have to do anything to make this so. This is “fate.” If you lose your job because the company goes bankrupt and everyone is laid off, this is also fate since it is outside your control. “Nature,” on the other hand, refers here to the best self that a thing has the built-in (i.e., natural) potential to become. In this sense, it is an acorn’s “nature” to be an oak tree.
There are two things in particular that we should note. First, superior people refer only to our moral inclinations as “nature”; second, the physical inclinations themselves are also part of our “nature.”
This is obviously very compressed; here’s what’s going on. Both moral and physical inclinations arise in us on their own (think of the reaction to seeing a baby about to fall into a well) and so are “fated,” but the physical ones are much more robust than the moral ones. If we do nothing to nurture our moral reactions, they’ll remain weak and will rarely move us to action. This is why we need to “cultivate” our sprouts. Physical reactions, on the other hand, don’t need our help. Sure, you can cultivate a taste for something new or learn to appreciate subtle distinctions of flavor, but even without this, you’ll enjoy food. So superior people focus their efforts on the moral reactions, and Mengzi signals this by saying they don’t actively think of the physical ones as “nature.” Still, physical satisfactions are nonetheless part of our nature, part of our best lives. Living a good Confucian life involves physical pleasures as well as moral ones.