We know that in his formulation of the Christian faith Pere Teilhard, seeking for greater fidelity to the thought, the tactical sense, and the very words of St Paul, would have liked to win acceptance for the expression "Christian pantheism",* as opposed to all the "false pantheisms", whether new or old, Eastern or Western, crude or subtle. Sometimes he risked using the words, explaining them, however, in a way that made any wrong interpretation impossible. Occasionally one feels that it went against the grain to have to refrain from doing so. There are other passages in which he simply contrasts the Christian or the "guest of the divine milieu" with pantheist. In any case, quite apart from the actual terminology, there can be no doubt that of all contemporary thinkers it was Teilhard who was the most outspoken opponent of pantheistic concepts of Godhead. He vigorously rejected every type of "pantheist bliss". In every doctrine, whatever might be said for it in other respects, that describes the "final state" as "a faceless organism, a diffuse humanity,—an Impersonal" he denounced its "betrayal of the Spirit". On one occasion he spoke of the "triumphant joy", retained even in his "worst hours", that he drew from his faith in the transcendence of God. At the same time he held that "we must love the World greatly if we are to feel a passionate desire to leave the World behind"... He knew also that "the false trails of pantheism bear witness to our immense need for some revealing word to come from the mouth of Him who is"... He sought, too, to do more than reject or refute pantheism: by establishing the "differentiating and communicating action of love",† he neutralized its temptation.
What perhaps introduces some confusion into this subject is that too many people in our modern West, even including some who are extremely firm in their faith and heedful of the spiritual life, are apt to forget the divine Presence and the divine Action in all things—even indeed at the natural level. It is here that a superficial cult of the spiritual has done a great deal of damage. Just as many, when they have to consider their final end, can only oscillate "between the concept of an individual survival that leaves beings isolated from one another, and a reflection that absorbs them into the one", so the divine transcendence is too often conceived, or rather imagined as itself, too, being purely exteriorized. As Pere Abel Jeanniere has said, "Among many who are opposed to the thought of Teilhard we find an underlying mental attitude which allows no possibility of distinction except in separation and mutual exteriority." It was of these people that the author of the Milieu Divin was thinking when he said: "Of those who hear me, more than one will shake his head and accuse me of worshipping Nature." In fact, "however absolute the distinction between God and the world (since everything in the world—and the world itself—exists, even at this present moment, only by divine creation), God is present in the world and nothing is more present in it than the God who creates it: for 'it is in him that we live, and move, and have our being'". Deus non creavit, et abiit (St Augustine.)
* Cf. Mgr. Lucien Cerfaux, Le Chretien dans la Thiologie pauhnienne (1962), p. 212, on 1 Cor. Is. 28: "The ancient Stoic formulas, pantheist in tone, the identity of the one with the whole, God all in all, are Christianized. Personal monotheism asserts itself. ..." Or again, Edgar Haulottc, S. J., L'Lsprit de Yahme dans l'Antsen Testament (in the symposium L'Ilomme ileums Dieu, 1964, I, p. 28) on Acts t 8.24-9: Paul "puts the language of the Bible into words that can be understood by the Epicureans and Stoics to whom he is speaking. ... He relieves 'the whole', 'the one', 'the origin', 'life', 'breath', from the implication they have in Stoic thought with impersonal cosmic forces; instead, he brings these realities into the same circuit, so to speak, as the personal creative force of God."
† One cannot help seeing here a kinship of thought with Maurice Blondel. In the same year as Pere Teilhard was writing Le Christ dans le Matiere, Blondel was writing to Pere Auguste Valensin: "I can no longer remember very well the arguments you remind me of in connection with the Catholic antidote (through the Eucharist) for the terrible evil of pantheism. I was trying, no doubt, to show the strength of that pernicious doctrine, precisely because of the profound sense it shows of the problem of in some way getting the finite and the infinite to cohere and live together. And it is to escape both a baneful immanentism and a frigid, unintelligible, incommensurable, transcendentalism that one can find (as a Catholic, not spontaneously as a philosopher) an illuminating sweetness in the Verbum Caro, which affirms the distinct absolute reality both of God and of the creature, and their most intimate union" (5 April 1916). Earlier, on 30 Oct. 1915, Blondel wrote: "It is the first and last temptation of all who refuse to receive the word of God."
Henri de Lubac - Teilhard: the man and his meaning (1965), p. 21-23
I'm reading Lubac's book alongside The Divine Milieu to help myself process the harder bits of Teilhard as I go. The very sound of the phrase "Christian pantheism" is shocking, if not actually scandalous, but I find the concept as described by Lubac and Teilhard both uplifting and edifying. The incorporation of the Incarnation into the argument by Blondel in the second footnote is key, I think, since the whole thing must hang on that.