Perhaps Cusa's most stunningly consequential claim in OLI is the following:
"The world has its center everywhere and its circumference nowhere, for its circumference and center is God, who is everywhere and nowhere."This provocative vision of a centerless, edgeless cosmos contradicts the Aristotelian/Thomistic/Neoplatonic hierarchical cosmos, the "Great Chain of Being" that dominated medieval thought, and which served to justify ecclesial hierarchy. Now, after Cusa, all is equally a perspectival center, and not merely the earth. Furthermore, the cosmos no longer has a spatio-temporal limit - contra medieval cosmologies, which imagined the stars to be the cosmic circumference.
Thus for Cusa, nothing finite has metaphysical priority, for all are equally finite, or equidistant, in relation to the infinite. And since all things are their own perspectival centers - and because absolute equality is attributed only to God, the absolute Maximum and Minimum - all things are irreducibly different from each other: "two or more objects cannot be so similar and equal that they could not still be more similar ad infinitum." But each thing - human or nonhuman - is also an image of the infinite God, who communicates being and form to all "without envy," even as the creature can only receive it in a finite way. Thus, each thing is now seen by Cusa to be perfect in its own distinct way. He even calls every creature a "created god" or "finite infinity."
Cusa thus overturned the heterogeneous cosmos in which diverse elements become increasingly "noble" and "pure" as they ascend the ladder of being, replacing it with a homogenous cosmos of equally perspectival and uniquely valuable singularities. It seems to me that modern and postmodern science, philosophy, and theology have continued to validate (or echo) many of Cusa's related ideas in a number of ways:
First, Cusa's cosmology anticipates Copernicus by more than a century, who placed the sun rather than the earth at the cosmic center (i.e., heliocentrism replaces geocentrism). But Cusa went further, claiming that nothing is at the physical center of the cosmos, because God is omnicentric, and creation (as derived from God) images or imitates God "as much as possible." Thus, it too is (metaphysically) omnicentric - although, from another (physical) perspective, its center is "nowhere," since its center is God.
Second, if there is no absolute cosmic center, there is no cosmic circumference, so the universe is spatio-temporally limitless, endlessly becoming, or "contractedly infinite." Creation thus reflects God, who is imagined by Cusa to be an infinite circle in which center and circumference coincide. An omnicentric cosmos is also "one" from a certain perspective (as enfolded in God), and "many" from another perspective (as unfolded from God). These insights anticipate contemporary theories of the multiverse and cosmic infinity - but again, Cusa's views are based primarily on theological speculations rather than empirical observations. (I'll also mention that, in some ways, it anticipates William James' lectures on "A Pluralistic Universe").
Third, since there is no absolute physical center, and since only God is absolute equality while we as perspectival creatures endlessly differ, there can be no absolute (non-perspectival) standard of measurement/comparison between things. Since human knowledge is based primarily on measurement/comparison of proportions, there are two profound consequences of this - one epistemological and the other cosmological:
1) All knowledge about the physical universe is always necessarily "conjectural," since nothing can provide a non-perspectival standard of comparison between things, and no two finite things could ever be absolutely equal (again, only God is absolute equality).
2) All things must be in motion, since an immobile center at absolute rest is required to measure things in motion (furthermore, only God is absolute rest).
Consequence 1 anticipates post-Kantian philosophy's emphasis on the radical limits of knowing, which dominates nearly all Western thinking down to the present. Consequence 2 anticipates Einstein's special theory of relativity, which says that all rest and motion are entirely relative to the standpoint of the observer.
Fourth, a centerless cosmos means that all religious claims are perspectival symbols or metaphors that are relative to creatures. They cannot capture God in Godself. Even the Trinitarian names are creaturely metaphors - which are necessary for communal worship, but more importantly, they must be negated to avoid idolatry. Cusa even goes so far as to say that we project ourselves on to God, so that if a lion were to imagine God, it would imagine God like a lion; just as we imagine God in human terms (e.g., Father, Son). Thus, a high degree of tolerance for different and contingent expressions of faith is necessary, and he recommends a dialogical approach to religious differences in order to maintain peace. As a cardinal of the Church, Cusa did not renounce a Christocentric orthodoxy in saying these things. Yet there is obviously something deeply subversive about his approach that enables a more flexible and humble style of religious belief.
Again, these conclusions are based purely on a speculative theology of "learned ignorance" that rigorously holds to the qualitative difference between the infinite and finite. Everything unfolds from that presupposition. Since human knowledge is based on comparing proportions between things - which is quantitative - the infinite cannot be known. And because the finite logically coincides with the infinite (lest the infinite be limited by something external), Cusa ultimately argues:
"God, therefore, is the enfolding of all in the sense that all are in God, and God is the unfolding of all in the sense that God is in all."Thus in God's infinity, all opposites are enfolded, including knowledge and ignorance. This is precisely why Cusa maintains that we can only gain some knowledge about reality by first maintaining that we are totally ignorant, by recognizing the profound limits of knowing - not just about God, but about creation as well. Amazingly, ignorance and knowledge coincide as Cusa unfolds a radically relational and perspectival cosmology.
Lastly, in the above quote, Cusa gives us one of the first significant expressions of panentheism in Western theology. His concept of God culminates with the metaphor of God as posse ipsum, or possibility itself. This marks a sharp break from scholastic theisms that privileged actuality over possibility, since the latter is conceived as a 'lack'. But a God of pure act and pure presence is highly deterministic, while a God who is infinite possibility - who 'possibilizes' - is open-ended and continually arrives out of the future. Thus, Cusa ends his speculative theology by claiming that this is the best metaphor for God: the presupposed 'can-do', the enabling divine potentiality for every actuality. Not unlike process theology that developed in the 20th century, Cusa sees each actual creature as 'contracting' the whole interrelated universe, including possibilities, to freely become what it is. Cusa's final panentheistic vision is therefore of a dynamic God who "may-be" (Kearney), not omnipotent, but "omni-potential"(Keller).
For further reading on Cusa (secondary sources), I recommend the following:
-Cloud of the Impossible, by Catherine Keller (chapter 3)
-The Individual and the Cosmos, by Ernst Cassirer (chapter 1)
-World's Without End, by Mary Jane Rubenstein (chapter 3)
-Introducing Nicholas of Cusa, edited by Belitto/Izbicki/Christianson