Section 4 addresses the case of an incapacitated president who is unable or unwilling to execute the voluntary declaration contemplated in Section 3; it is the amendment's only section that has never been invoked. It allows the vice president, together with a "majority of either the principal officers of the executive departments or of such other body as Congress may by law provide," to declare the president "unable to discharge the powers and duties of his office" in a written declaration. The transfer of authority to the vice president is immediate, and (as with Section 3) the vice president becomes acting president – not president – while the president remains in office, albeit divested of all authority.[6]