The president may require the "principal officer" of any executive department to tender his advice in writing. While the Constitution nowhere requires a formal Cabinet, it does authorize the president to seek advice from the principal officers of the various departments as he (or she) performs their official duties. George Washington found it prudent to organize his principal officers into a Cabinet, and it has been part of the executive branch structure ever since. Presidents have used Cabinet meetings of selected principal officers but to widely differing extents and for different purposes. Secretary of State William H. Seward advocated the use of a parliamentary-style Cabinet government to President Abraham Lincoln, but was rebuffed. Later, Woodrow Wilson advocated use of a parliamentary-style Cabinet while he was a professor, but as president he would have none of it in his administration. In recent administrations, cabinets have grown to include key White House staff in addition to department and agency heads. President Ronald Reagan formed seven subcabinet councils to review many policy issues, and subsequent presidents have followed that practice.