At least two different meanings of the term "nature" may be found in Italian art theory in the 15th century. When Lorenzo Ghiberti tells us that he "strove . . . to endeavor to imitate Nature in [the stories of his second Baptistery door] as much as [he] might be capable," or when Leon Battista Alberti stresses the special power of the face drawn from nature, which "will draw to itself first of all the eyes of one who looks," and concludes, "For this reason always take from nature that which you wish to paint, and always the things will turn out more beautifully," they mean by the term "nature" the reality of our daily experience. Let us call this the passive meaning.
But at the same time both Ghiberti and Alberti use this term in what we should like to call an active meaning. Ghiberti, in the same autobiography, says, "In order to master the basic principles [of art] I have sought to investigate the way nature functions in art." Alberti begins his moving dedication to Brunelleschi of the Treatise on Painting with the pessimistic opinion he once held, that many of the arts famous in ancient times were lacking in his time, and continues, "Thus I believed, as many said, that Nature, the mistress of things, had grown old and tired. She no longer produced either geniuses or giants, which in her more youthful and more glorious days she had produced so marvelously and abundantly." They are using the term "nature" in this active meaning, and they mean by this word a live power that directs and governs life in men, animals, and plants, as well as the growth of a work of art.
This double meaning of the concept of nature originated in Greek thought, although some other meanings have been connected with this term as well. It is true that Anaxagoras, the Atomists, and Aristotle conceived nature as the reality accessible to the senses. For the Stoics, Nature was identical with the life-giving power, and this equation Natura sive Deus will, after centuries, recur in the pantheistic and dynamistic ideas of the Renaissance.
The concept of the imitation of nature was deeply rooted in the classical philosophy of art; mostly the imitation of created nature (natura naturata) was meant, but the second concept, that of the imitation of creating nature (natura naturans in medieval terminology) appeared quite often. This conviction was expressed, for instance, by Democritus, who saw in the human arts an imitation of nature in action. In the Neo-Platonism of Plotinus this idea has been developed: "If somebody does not esteem the arts because they imitate nature, it should be said first that nature herself imitates. Then it should be borne in mind that the arts do not simply copy the visible things but draw from the principles that constitute the source of nature." This active meaning of the concept of nature in relation to art may be found as early as Heraclitus, who compared the method of composing harmony of opposed elements visible in the activity of nature to the working method of the arts, which "operate in a similar way, imitating nature."
Medieval thought continued to use both these concepts of nature, and it developed, especially in the philosophy of Johannes Scotus Eriugena and of the Averroists, the concept of natura naturans, which had been introduced in antiquity. According to St. Thomas Aquinas, the visual arts imitate the visual aspects of created nature as well as nature's way of operating, directed to a definite purpose: "All nature is aiming at her end, since she aims through definite means to certain ends, and just this is imitated by art in its actions.'" Similar ideas may be found in Italian writings of the 14th century, on the threshold of the Renaissance. Boccaccio, in his Genealogia deorum, writes that Epimetheus made a human figure ad instar naturae -"by his desire to copy nature he imitated the nature of the ape and was therefore called an ape himself." Here nature is meant first in the passive, and second in the active, meaning. The implication is that the artist in imitating nature only follows Nature's own command, since she herself has endowed the apes . . . with the imitative instinct."
In the 15th century, finally, the simple, natural appearance of real things in the world that surrounds the artist - "il naturale" - is one aspect of nature. The other one is formed by the concept of a mighty power, of natura naturans. Alberti employs this second concept when he calls nature "marvellous artificer of things" and says that "nature herself seems to delight in painting." This concept allows him to consider architecture as an art that imitates nature (although it does this in a way different from that of painting and sculpture). Alberti develops this concept without, however, giving it enough unity and consistency. Sometimes he takes an animistic turn, as when he quotes classical authorities to the effect that a building is like a living animal, and that when giving it its final form, the work of nature should be followed. Sometimes he conceives nature again as a living and creating power: "The Ancients . . . did in their Works propose to themselves chiefly the Imitation of Nature, as the greatest Artist at all Manner of Compositions; and for this Purpose they laboured, as far as the Industry of Man could reach, to discover the Laws upon which she herself acted in the Production of her Works...." And in this last sentence Alberti stresses at the same time not only the creative character of nature but her way of acting according to certain laws as well. His idea is the same in the Treatise on Painting: "I will enlarge on the art of painting from its first principles in nature." Alberti then tries to establish which laws are being followed by nature as she strives toward perfection. By introducing this approach to his theory of architecture, he opened the age of architectural theory that was conceived as a discovery of unique and general aesthetic laws, inherent in nature. Accordingly, the theory of architecture for a long time was treated as a part of the study of nature and of the discovery of her laws.
"It is manifest," Alberti wrote, "that Nature delights principally in round Figures, since we find that most Things which are generated, made or directed by Nature, are round." But this is a specific question. The most general law is that of concinnitas, of harmony, or, as Leoni's English translation puts it, of "congruity": ". . . every Part and Action of Man's Life, and every Production of Nature herself . . . are all directed by the Law of Congruity, nor does Nature study any Thing more than to make all her Works absolute and perfect, which they could never be without this Congruity."
But the idea of the perfection of nature, implied by the conception quoted above, is partly contradicted by Alberti, who quotes Cicero to the effect that "nothing is at the same time both new born and perfect," and in the Ten Books on Architecture says that "it is but very rarely granted to any one, or even to Nature herself, to produce any Thing every Way perfect and compleat." So, an artist should select from nature the most beautiful parts, in order to avoid imperfections that may be found in natural things. It follows that, thanks to this selection, a work of art may happen to be more perfect than a work of nature. For Thomas Aquinas, nature had her own beauty, although the eternal beauty was superior to hers. But medieval writers always considered nature as a divine creation superior to human art. Human art could never, until the Renaissance, have been considered as surpassing nature. It was St. Augustine's opinion that the beauty of nature reflecting the spirit of the Creator cannot be approached by man's efforts. For Dante, human art was only a child of nature and a grandchild of God. Art may perhaps approach nature, but not surpass her. Grosseteste wrote: "As art imitates nature and nature acts always in the best of all possible ways, therefore art is also as infallible as nature."
Both imitation of natura naturata and of the creational powers of nature have been known to previous times, but in supposing that an artist who creates a work of art is able to achieve a greater perfection than nature in her work has ever achieved, Alberti formulated a new idea of great importance. Nature is perfect as a harmonious whole, to be sure, but her elements are not: this idea can be deduced from the famous anecdote quoted by Alberti about Zeuxis selecting the most beautiful parts of the five most beautiful girls of Croton.
At the end of the fifteenth century the position of nature in the theory of art was attacked from two sides. For the Neo-Platonists, nature was opposed to mind: for the Neoplatonist Marsilio Ficino in Florence, nature was the lowest degree of being, beneath "grace," "providence," "destiny"; nature was for him the last element in the chain that connects the world of form with the world of matter. This important school of thought probably had its share in demoting nature from the position she held in fifteenth-century aesthetics. Natura naturata is now being considered as full of shortcomings, as a low stage of being. The interest goes in two directions. The active concept of nature is now being developed and transformed and given an animistic, magical turn on one hand, and a creational turn on the other. In the naturalistic philosophy of Telesio and Patrizzi, in the writings of Paracelsus and Sebastian Franck, the knowledge of nature means becoming identical with nature. Nature is understood as a living unity, parts of which are connected by innumerable links: "God created the world as a living, animated, and intellectual being," Ficino said.
Reflections of this doctrine, which conceives the world as an animated being, are found in Italy in Leonardo: ". . . we might say that the earth has a spirit of growth...." But, in spite of several connections of Leonardo with this organic conception of nature, these utterances of his are perhaps not the most typical of his outlook as a whole. His thought was affected by another trend, also fed by Neo-Platonic speculation: the tendency toward mathematical generalization of empirical experience. The impact of this tendency was much more visible on Italian artistic practice in the High Renaissance and in Mannerism. For Leonardo, knowledge of nature is based not only on the direct sense of life but, in a still higher degree, on the mathematical principles deduced from or coordinated with the observation of nature. Nature includes the principle of necessity, which governs her life and development: Nature is governed by reason as by its indwelling law. Reason is nature's master and protector, her bridle and eternal norm." Now nature is meant not so much as the reality of visual experience and not so much as a divine or irrational power holding sway over human life; now it is meant first of all as a cosmic system, constructed of principles, of laws, that govern the evolutions of celestial bodies, as well as the growth of plants. The term "nature" did not mean now an inherent magical power, but rather an order discovered by the searching mind and an analytical eye.
For Alberti, imitation was first. For Leonardo, it is replaced by creation based on knowledge of necessity and inherent laws of nature. Nature, rejected as brute matter by the Neo-Platonists, has been ennobled by Leonardo, who saw in her a realm of perfect form and of proportion. The process of evolution turned toward classical antiquity. Now the artist was to look for his source not so much among the elements of natura naturata, but among the works of perfect art of the ancients, which had been created according to the necessary and general mathematical laws, reasons, and proportions inherent in nature. Classical artists had discovered and shown in their works the reasons that constitute the basic foundations of nature in her purest form and, thus, they help the modern artist to surpass nature.
In his biography of Mantegna, Vasari wrote: ". . . he showed that he knew how to take the good from living and natural objects as well as from those created by art. But with all this, Andrea always believed that good classical statues were more perfect and possessed more beautiful parts than is shown by nature, because those excellent masters, according to what he judged and what he has seen in those statues, had taken the perfection of nature from many living persons...." Instead of selecting the best from nature, as Alberti had advised, the artist now preferred to look at the ideal art, which had already made the necessary selection. At the same time the superiority of the beauty of art to that of nature was firmly established. The thesis was formulated, to use Erwin Panofsky's words, "that classical art itself, in manifesting what natura naturans had intended but natura naturata had failed to perform, represented the highest and 'truest' form of naturalism."