1. Whether Title VII's retaliation provision and similarly worded statutes require a plaintiff to prove but-for causation (i.e., that an employer would not have taken an adverse employment action but for an improper motive), or instead require only proof that the employer had a mixed motive (i.e., that an improper motive was one of multiple reasons for the employment action).

2. Whether the statutory phase discrimination based on age includes retaliation based on the filing of age discrimination complaint

Whether Title VII's retaliation provision requires but-for causation or mixed-motive standard for proving employment discrimination