It depends on how you define Panentheism. You can take the word at face value, and then put anything into it that can fit that definition. That is what Wikipedia does, and it strikes me as very suspect. Certainly the inventor of the word didn't mean it that way - he meant to strike out a different religious philosophy different from Pantheism.
If you take the word at face value, it means:
- Pan - all
- En - in
- Theism - G-d.
This is distinct from Pantheism where All is G-d - in other words G-d is the sum of the universe and nothing else, which is more reminiscent of the Arabs that worship the dust of their feet that Rashi speaks about.
That idea of Panentheism (that it means what the word roots say) maps with the Medrash that Yahu explores here, using that expanded definition (as defined by Wikipedia).
However, that isn't what Panentheism really means. Panentheism, as Miriam-Webster so succinctly defines means:
- the doctrine that God includes the world as a part though not the whole of his being
That violates many doctrines of Judaism, including non-corporeality, G-d's Oneness, creation ex-nilo, etc.
However, to discuss the larger Wikipedia definition of Panentheism in a Jewish context, you could say that everyone that says the Tzimtzum is not literal (which emphatically includes the Ba'al HaTanya, but others as well - in fact some deny the Gr"a ever held differently, so they clearly don't hold that way, whatever the Gr"a held), which means that G-d transcends the world, and there is no place in the world where He is not present.
If you want to call that Panentheism, I guess you can, but it really bears no relationship to the philosophical/religious ideas that actively identify themselves with the word. Those ideas, from what I read (and see the links in this post) seem to all be about how the world is part of G-d, G-d is changed by the creation of the world, so in some way (apparently much like the Rambam describes the evolution of Avodah Zarah, each one comes along with a new twist) the world is part of an interactive system within G-d.
In the Tanya, the whole argument that G-d transcends the world is that G-d is unchanging and unchanged:
ועל כרחך אין ידיעתו אותם מוסיפה בו ריבוי וחידוש, מפני שיודע הכל בידיעת עצמו
and perforce His knowledge of them does not add plurality and innovation to Him, for He knows all by knowing Himself.
Were G‑d’s knowledge of created beings not to come from knowing Himself then it would be correct to say that this knowledge adds plurality and innovation to Him; previously He did not know them and now he does. However, since plurality and innovation cannot possibly apply to G‑d, He must perforce know them through His knowledge of Himself.
הרי כביכול מהותו ועצמותו ודעתו הכל אחד
Thus, as it were, His Essence and Being and His Knowledge of created beings are all one.
Since G‑d’s knowledge and Providence extend to this world, and since His knowledge is one with Him, it follows that G‑d Himself is to be found within this physical world. Unlike the king who sits in his palace and gazes beyond its walls, the King Himself is to be found wherever His Providence and knowledge are found.
True enough, it is only through divine service that this world may be transformed into a place in which G‑d is revealed. Nonetheless, G‑d is present in this lowly corporeal world, which feels itself to exist independently of Him, to the same degree as He is present within the higher spiritual worlds.