Definition
In Stoic ethics, only virtue is good and only vice is bad. Everything else — health, wealth, reputation, comfort — falls into the category of "indifferents," meaning it cannot make a person good or happy on its own. Yet the Stoics did not treat all indifferents alike. They distinguished things that accord with our nature and are worth pursuing from things contrary to it.
Preferred indifferents are those externals — health, sufficient resources, a sound reputation — that have natural value and that a reasonable person selects when free to do so. They are still indifferent because losing them does not damage one's character, but they are "preferred" because choosing them is the rational default.
Why it matters
How it works
When you face a choice, you select the preferred option — the job, the treatment, the safer route — because that is what reason recommends. But you hold the result loosely. If circumstances deny it, no harm reaches your character, because your good was never located in the external.
The complementary category, "dispreferred indifferents" such as illness or poverty, is reasonably avoided by the same logic. The art lies in pursuing wisely while remaining unshaken by loss, a stance the Stoics called acting with a "reserve clause."