Shaykh al-Akbar Imam ibn Arabi al-Hatimi at-Tai termed this concept "the Unity of Existence" — al-Wahdat al-Wujud.
A common argument against the concept of al-Wahdat al-Wajud, often brought up by the Wahhabi Muslims or the Ahl-e-Hadith, the likes of Dr. Zakir Naik and Dr. Bilal Philips, is that it is Shirk in the form of Pantheism. Untrue.
Pantheism is the belief that God is Present in Creation in the physical sense, and is thus worshiped. This leads to paganism and idolatry as the objects in creation are directly worshiped as containing the Essence of God. In other words, Pantheism reduces God bound to three-dimensional entities existing within space and time inside creation.
In sharp contrast, Wahdatul-Wujud enhances God beyond any space, time or dimensional boundaries by stating that if everything in being was extended to infinity, nothing would remain but God. That is, a two-dimensional picture of a house can be rendered into three-dimensions whence it would take the form of an actual house with height, weight, width and length. However, if everything in existence now, similarly, be rendered to infinite dimensions then it would all cease to exist except for God. Therefore, in the greater scheme of things, we conclude, nothing exists but God.
This is the Ultimate Truth. This is the Unity of Creation and All of Existence. This is Wahdat al-Wujud.