This valuable treatise decribes the far-reaching movement and revolutionary reform of the greatest mystic Shaikh Ahmad Sirhindi, well known as the Mujaddid Alf Thani or the renewer of the second millennium of Islamic era. The main theme of this thesis dominates the Mujaddid's conception of Tawhid known as Wahdat-i-Shuhud, which was presented to contradict the widely accepted doctrine of Ibn Arabi's Wahdat-i-Wujud or unityism. Mujaddid's oppsition is not based on theological dogma but on direct mystic experience, which turned the tide, entirly, to the original Islamic teachings based on the works of the scholars of Ahl-as-Sunnah. This work also includes the scholarly receptions of this new doctrine by both mystics and theologians of outstanding eminence such as Shah Wali-Ullah Dehlwi and Sayyid Ahmad Barelwi, which are very interesting and helpful for deep study and careful scrutiny of Islamic Sufi philosophy.