Final answer:
Rawls's veil of ignorance requires individuals to omit knowledge of their personal circumstances to design a just society, but uncontroversial facts about human psychology and economics may not need to be excluded.
Step-by-step explanation:
According to Rawls, morally irrelevant information about personal circumstances such as economic status, education, health services access, talents, abilities, gender, race, and class need to be placed behind the veil of ignorance. This ensures that when imagining the original position, no individual knows these details about themselves, facilitating the design of a just society free from such biases.
What may not be necessary to place behind the veil of ignorance are facts that are uncontroversial about human psychology and economics. The rational individuals participating in the original position should retain knowledge that doesn't give them an advantage in the social structure they aim to design, allowing them to consider systems that benefit everyone fairly.