Nicholas of Cusa was both a man of action and a man of speculation. He spent his years in the Roman Catholic Church working for the cause of reform and ecclesiastical diplomacy; he was a Cardinal and Bishop of Brixen. As a metaphysical theologian, he synthesized the ideas of such predecessors as Johannes Scotus Erigena, Meister Eckhart, and pseudo-Dionysius the Areopagite. His work had a considerable influence on Giordano Bruno, particularly on the latter’s De la causa, principio e uno (1584; Concerning the Cause, Principle, and One, 1950).

Of Learned Ignorance, Nicholas’s most important treatise, is particularly interesting as an attempt to reconcile the Neoplatonic ideas prevalent in the Middle Ages with the growing confidence in empirical inquiry and the use of the intellect. The reconciliation is only partly successful from the logical point of view, and it involves an appeal to the revelatory power of mystical intuition. However, for those who sought to understand the possibility of unifying an infinite God and an apparently finite universe and who were disturbed by their learned ignorance, the efforts of Nicholas of Cusa were a godsend.

The work is divided into three books and is unified by a concern with the maximum, the greatest. The first book is a study of the “absolute maximum,” or God, the being who is greatest in the sense that he is one and all—all things are in God, and God is in all things. Nicholas describes this study as one “above reason,” and as one that “cannot be conducted on the lines of human comprehension.” The second book is concerned with the maximum effect of the absolute maximum. The maximum effect is the universe, a plurality that is, nevertheless, a relative unity. The third book is devoted to the maximum that is both relative and absolute, the perfect realization of the finite plurality of the universe; this maximum is Jesus.

Nicholas begins his work by explaining that people have a natural desire for knowledge but are frustrated in their desire to know by the enduring fact of their own ignorance. People strive to understand what is not understandable—for example, the infinite as infinite, which is beyond comparison. The only solution, then, is for people to seek to know their own ignorance, even as Socrates advised. If people make their own ignorance the object of their desire for knowledge, they can acquire a learned ignorance. The suggestion is that from reflecting on their limitations people can, in knowledge, surmount their own ignorance, at least to some extent.

Finite intellects proceed by comparisons, according to Nicholas; and it is on that account that the Pythagoreans came close to the truth in saying that it is by numbers that all things are understood. However, if the effort is to understand the absolute infinite, the means of comparison will not work, for the absolute infinite is beyond comparison. To realize that the quiddity of things, the absolute “whatness” of them, is beyond our intellects—and that, in regard to the truth about ultimate being, one must be ignorant—is to draw closer to truth.

If one cannot comprehend the absolute maximum (which is God), then what is the point of working out the implications of the conception of the absolute maximum? Nicholas argues that although one cannot comprehend the absolute maximum, one can have some knowledge about it. One can know, for example, that the precise nature of the absolute maximum is beyond one’s powers of understanding. However, there is more than that which one can know.

One can also know that the absolute maximum is also the absolute minimum. Nicholas proves this point in an engaging and simple argument: “By definition the minimum is that which cannot be less than it is; and since that is also true of the maximum, it is evident that the minimum is identified with the maximum.” There is another good reason for supposing that the maximum and the minimum are synonymous: Because the absolute maximum is actually all that it can be, it is both as great as it can be and as small as it can be. Because it is the absolute, it can be absolutely minimum as well as absolutely maximum, and because it can be, it is. Furthermore, the maximum considered in itself, not as the maximum of a certain matter or quantity, is the infinite. However, so is the minimum. Because both the maximum and the minimum are the infinite, they are one. The maximum is absolute unity, for unity is the smallest number, or the minimum; God is a unity that “excludes degrees of more’ or less,’” and is, consequently, an infinite unity.

Nicholas introduces his version of the cosmological argument: Finite beings are effects that could not have produced themselves; therefore, there must be an absolute maximum, not itself dependent on causes, without which nothing else could exist.

The conception of the Trinity is introduced by an elaboration of the Pythagorean idea that unity is a trinity. Diversity involves unity (two, for example, is two ones); inequality depends on equality (and, therefore, on unity); and connection depends on unity, for division is a duality or involves duality. Diversity, inequality, and division necessarily involve unity, equality, and connection; and the latter three are all unities, but unity is one. Unity is a trinity, since unity means nondivision, distinction, and connection.

According to Nicholas of Cusa, the visible world is a reflection of the invisible. By the use of conjectural images, people can, at least to some extent, mirror the eternal and infinite. The images most helpful to people are mathematical images, for, as Pythagoras pointed out, “the key to all truth [is] to be found in numbers.”

The symbols that Nicholas found most useful in suggesting the nature of the absolute maximum are the line, the triangle, and the circle. An infinite line, according to Nicholas, would be at once a straight line, a triangle, a circle, and a sphere. He argues, for example, that as the circumference of a circle increases, the line becomes less curved; and he concludes that the circumference of the absolutely greatest possible circle would be absolutely straight, the smallest possible curve. (Although logically there is an essential difference between a curve, however slight, and a straight line, Nicholas’s figure, considered as a metaphor, achieves the purpose of suggesting that entities disparate in character are nevertheless such that, when taken to infinity, they are indistinguishable.)

A finite line can be used to form a triangle, he argues, by keeping one end fixed and moving the line to one side. (Actually, the figure so formed is not a triangle, but a segment of a circle, a pie-shaped segment.) If one continues the movement of the line (so that it functions as an infinite number of radii), the figure formed is a circle. Half a circle, if turned in three dimensions on its axis, forms a sphere.

An infinite triangle would have three infinitely long sides; infinitely extended, the triangle would finally be indistinguishable from a line. Such a triangle would have three lines in one and in that respect would resemble the infinite absolute maximum (God). Apparently Nicholas conceived of a triangle’s sides as increasing and its base angles, say, as becoming more acute and the apex as becoming more and more obtuse, until finally there would be no triangle distinguishable from a straight line. However, he need not have conceived of it this way. He could have conceived of a triangle expanding while its angles remain constant. Part of Nicholas’s argument, however, depends on the assumption that there cannot be more than one infinite. To maintain this point involves a peculiar use of the term “infinite.”

Having demonstrated to his satisfaction that an infinite line is a triangle, a circle, and a sphere, Nicholas develops the image to suggest by analogy the relationship of the absolute maximum to all things: The infinite line is to lines what the absolute maximum is to things. The analogy is developed at great length, but the most important features are these: An infinite line is not divisible; it is immutable and eternal. Oddly, it shares its essential features with finite lines—for finite lines, for example, cannot be divided into anything other than lines and are, in that sense, indivisible. Just as the essence of an infinite line is the essence of all finite lines, so the essence of the absolute maximum is the essence of everything. This point is developed by reference to beings who have only a participation in being. Because the essence of such beings is the essence of the absolute maximum, once the feature of participation is eliminated, the distinction between beings that participate in being and the being in which they participate disappears.

Again, by mathematical analogy, Nicholas argues that there could not be four or more divine persons; there must be a trinity. A four-sided figure is not the smallest, simplest measure of things, as is the triangle. A circle, having neither beginning nor end, being perfect, possessing unity, and so forth, is an ideal figure of the divine. Nicholas thus comes to one of his characteristic contentions: “In the Providence of God contradictories are reconciled.” God’s providence includes all that shall be together with all that shall not be. God has foreknowledge of everything, for he foresees opposites. The absolute maximum is in all beings, and all beings are in it.

By the analogy of the infinite sphere, Nicholas argues that God is the “one infinitely simple, essential explanation of the entire universe.” He is the final cause of everything, the determiner both of existence and of end. All names attributed to the infinite absolute maximum are anthropomorphic; none is adequate as a name, for God is beyond distinctions.

Because God is ineffable, negative propositions are truer than affirmative ones. It is better to count on learned ignorance, as enlightened by God, than to count on positive knowledge. Nicholas proceeds, in the second book, to demonstrate the absolute effect of the absolute maximum. The unity and infinity of the universe are shown to be a consequence of that infinitude of matter that arises from its incapacity to be greater than it is. Because God is not jealous, because the essence of every created thing is his essence, and because he is essentially perfect, every thing is, in its way, perfect. The universe (and everything in it) is a principle and a maximum but in a restricted sense. The absolute maximum brings the universe into existence by emanation (a timeless outpouring of its essential nature).

Thus, everything is in everything, as the philosopher Anaxagoras said. Because God is in all things by medium of the universe, “all is in all, and each in each.” Of course, the universe is in each thing only in a contracted or restricted manner; in fact, the universe is contracted, in each thing, to whatever the thing is. The unity of the universe, which comes from the absolute unity of God, is a unity in plurality and is not an absolute but a relative unity. The universe is also a trinity as well as a unity, but just as it is a relative unity, so it is a relative or contracted trinity. The unity of the universe is a trinity in the sense that contraction involves a limitable object, a limiting principle, and a connection—or potency, act, and the nexus.

There are four modes of being: the absolute necessity, or God; the mode of being of things according to natural necessity or order; the mode of being of individuals; and the mode of being of that which is possible.

The soul of the world is a universal form that contains all forms, but it has only a contracted existence; forms are actual only in the word of God. However, it is possible to use the term “soul” in such a way that the soul and God are one. Every possibility is contained in the Absolute Possibility, God; every form (or act) in the Absolute Form, the Son of God; and every connecting harmony in the Absolute Connection of the Holy Spirit. The Father is potency; the Son, act; and the Holy Ghost, connecting movement. Thus, God, who is unity as well as trinity, is the efficient, formal, and final cause of all things; and the movements of the earth and stars are attributable to him, who is the center and circumference. In reflecting on the world and on the wonder of its arrangement, one cannot hope to understand God’s reasons; but in the wonder of him and in one’s learned ignorance one finds intimations of his light.

Jesus Christ is “the maximum at once absolute and restricted,” and to the defense and clarification of this description, Nicholas devotes the third book. Human nature is peculiarly suited to provide God with the possibility of a maximum that reconciles the infinite and the finite by being at once absolute and contracted. As sensible and intellectual, human nature is a microcosm, a world in miniature. Unlike other things that, raised to perfection, could easily become greater because of the inferiority of their natures, humanity is such that, if perfected, reveals the nature of all things as perfected. By joining the nature of humanity to the divine nature, God made possible the union of the absolute maximum and the nature of all things. In Jesus, God is both God and humanity.

The remainder of Nicholas’s work is a defense, in terms of his mystical metaphysics, of familiar dogmas: that Christ was conceived of the Holy Ghost and born of the Virgin Mary, that he was resurrected after the Crucifixion, that he ascended into heaven, that he is the judge of the living and the dead, that he redeemed all humankind. In this account, Jesus is God utilizing the nature of humanity and bringing it to perfection; Jesus is humanity made perfect in the image and essence of God. Because of Jesus, the Church comes into being, the fullest possible realization of the unity of the many “with the preservation of the personal reality of each, without confusion of natures or degrees.” Additionally, by Jesus, the union of the subjects and the Church is resolved into the divine unity. Thus, for Nicholas of Cusa, as for Bruno, God is the cause, the principle, and the One.