You can’t be rational yet rigidly maintain your terminal values’ immunity to rational argument.
Any argument that my terminal values should be one thing or another will itself be founded on certain assumed values. You can’t start from a value-neutral position and get to a value system from there.
If rational argument alone is enough to cause a change in one’s values, I can see only a few possibilities:
The changed values were instrumental values rather than terminal values. It makes perfect sense to modify instrumental values if one no longer believes that they serve the attainment of one’s terminal values.
The values were incoherent. The rational argument has shown that they are in conflict with each other, making it clear that a choice among them is necessary.
I was going to add the possibility of a value whose subject matter is found not to exist, such as religious values founded on a belief in a god. Some of those values may evaporate after one becomes convinced that there is no god. But even in that case I think one can argue that the religious values really served a more fundamental value—the desire for self-respect.
Any argument that my terminal values should be one thing or another will itself be founded on certain assumed values. You can’t start from a value-neutral position and get to a value system from there.
If rational argument alone is enough to cause a change in one’s values, I can see only a few possibilities:
The changed values were instrumental values rather than terminal values. It makes perfect sense to modify instrumental values if one no longer believes that they serve the attainment of one’s terminal values.
The values were incoherent. The rational argument has shown that they are in conflict with each other, making it clear that a choice among them is necessary.
I was going to add the possibility of a value whose subject matter is found not to exist, such as religious values founded on a belief in a god. Some of those values may evaporate after one becomes convinced that there is no god. But even in that case I think one can argue that the religious values really served a more fundamental value—the desire for self-respect.