Key Arguments

• Parfit imagines a technologically 'transparent' world in which lie-detection prevents deception; in such a world one might be able to show that, according to S, 'it would be rational for everyone to cause himself not to believe S' and instead 'to believe some other theory'.
• In this scenario S would be 'self-effacing': if we all believed S and could change our beliefs, then by following S we would cause ourselves to cease believing S, so 'S would remove itself from the scene' and 'become a theory that no one believed'.
• Parfit draws a conceptual distinction: 'to be self-effacing is not to be self-defeating.' A theory can recommend its own disappearance from people’s belief systems while still correctly guiding action toward what is best for them.
• He argues that, personifying theories, 'the aim of a theory is not to be believed, but to be true, or to be the best theory'; hence, losing all adherents does not show that a theory is not the best theory.
• Even in the self-effacing case, S is not failing in its own terms because, by hypothesis, 'each of us has followed S—done what S told him to do—[and] each has thereby made the outcome better for himself,' which is exactly what S prescribes.
• Thus, the property of being self-effacing—advising agents to abandon belief in the theory—is compatible with being the best theory of practical rationality.

Source Quotes

This would be easier if, as I supposed, the technology of lie-detection made us all wholly transparent. If we could never deceive each other, there might be an argument that showed that, according to S, it would be rational for everyone to cause himself not to believe S. Suppose that this was true.

If we could never deceive each other, there might be an argument that showed that, according to S, it would be rational for everyone to cause himself not to believe S. Suppose that this was true. Suppose that S told everyone to cause himself to believe some other theory. S would then be self-effacing. If we all believed S, but could also change our beliefs, S would remove itself from the scene.

S would then be self-effacing. If we all believed S, but could also change our beliefs, S would remove itself from the scene. It would become a theory that no one believed. But to be self-effacing is not to be self-defeating.

It would become a theory that no one believed. But to be self-effacing is not to be self-defeating. It is not the aim of a theory to be believed.

It is not the aim of a theory to be believed. If we personify theories, and pretend that they have aims, the aim of a theory is not to be believed, but to be true, or to be the best theory. That a theory is self-effacing does not show that it is not the best theory.

If we succeeded in doing what S told us to do, this would again be better for us. Though S would remove itself from the scene, causing no one to believe itself, it would still not be failing in its own terms. It would still be true that, because each of us has followed S—done what S told him to do—each has thereby made the outcome better for himself.

Though S would remove itself from the scene, causing no one to believe itself, it would still not be failing in its own terms. It would still be true that, because each of us has followed S—done what S told him to do—each has thereby made the outcome better for himself. Though S would not be failing in its own terms, it might be claimed that an acceptable theory cannot be self-effacing.

Key Concepts

• If we could never deceive each other, there might be an argument that showed that, according to S, it would be rational for everyone to cause himself not to believe S.
• Suppose that this was true. Suppose that S told everyone to cause himself to believe some other theory. S would then be self-effacing.
• If we all believed S, but could also change our beliefs, S would remove itself from the scene. It would become a theory that no one believed.
• But to be self-effacing is not to be self-defeating.
• If we personify theories, and pretend that they have aims, the aim of a theory is not to be believed, but to be true, or to be the best theory.
• Though S would remove itself from the scene, causing no one to believe itself, it would still not be failing in its own terms.
• It would still be true that, because each of us has followed S—done what S told him to do—each has thereby made the outcome better for himself.

Context

Central paragraphs of section 9, where Parfit develops the notion of a 'self-effacing' theory using S as the example, and argues that self-effacement is compatible with success in the theory’s own practical-rational terms.