Recent research on the seemingly staid subject of logic has revealed not only that certain topics in logic explained how inductive reasoning came about, but also that logic itself learned to create its own history in which logic arose from simple beginnings, but over time developed ever better ways of thinking, eventually becoming a progressive force in the history of thought. Furthermore, by the eighteenth century, the history of logic served as the structure for the history of philosophy, as well as an encyclopedia of knowledge known as historia literaria.
Although the importance of inductive reasoning to natural philosophy has been acknowledged, other research has shown that the tradition of inductive logic, which historians of the scientific revolution have identified as new, was actually developed by Aristotelian philosophers. The best known of these is the Paduan philosopher Jacobo Zabarella. His logic developed in part as a criticism of Florentine Neoplatonism and the medieval Scotist philosophy. This tradition of logic was taught not only in Italy but also in England, where logic texts by Zabarella have been found to have been used as school texts. Further, in Germany there remain today ninety-seven copies of Zabarella's Opera Logicae. This logic was then adopted by Bartholomew Keckerman for more elementary teaching and finally adopted again during the second half of the seventeenth century in Finland and Scandinavia after the Ramus vogue had run its course. Finally, at Jena, texts by Zabarella and the Coimbra commentators from Portugal were seen to be the beginning of a tradition of logic that led to the philosophy of John Locke (1632–1704) and Robert Boyle (1627–1691).
The best way to explain the difference between the Neoplatonic and Scotist approaches to knowledge and logic is to follow the debate around what is now considered a guiding logical and philosophical question between 1500 and 1750: What was the first thing thought? Was it the pure concept of an object or idea as defined by the Neoplatonists and some Scotists, that is, an idea conceived in the mind without recourse to the unreliable senses? Was it being, or ens, as Thomas Aquinas wrote? Or was it a fuzzy notion of a whole object or concept that needed to be examined, carefully defined and refined, and finally, when more was known about it, completely reexamined?
The great innovators of logic in the seventeenth century—Francis Bacon (1561–1626), Pierre Gassendi (1592–1655), Robert Boyle, and John Locke—continued and transformed this anti-Platonic, anti-Scotist tradition. These anti-Platonic philosophers held that there were two types of knowledge, divine and human, each with its own method. Divine knowledge was accessed through inspiration; human knowledge, or artificial knowledge, had to be learned through the senses. The anti-Platonists often quoted Aristotle as saying, "There is nothing in the mind that is not in the senses."
Many philosophers did work on inductive reasoning, beginning with the sixteenth-century Aristotelians Benedito Pereira in Rome and Zabarella in Padua. Their work was drawn upon and transformed by Bacon, Boyle, and Locke in England, Gassendi and his followers in France, and members of a new German school of philosophy known as eclecticism. The eclectics, like their counterparts in England and France, were both anti-Platonic and anti-Cartesian. They gave their tradition a historical dimension, writing that since no human being could know everything, philosophers should examine the reasoning of past philosophers, criticize or accept the methods they had used to reach their conclusions, and finally judge the validity of the original concepts. Using improved logic, each philosopher would then add new information to explain his findings. Eclecticism also referred to a Neoplatonic philosophy that tried to unify all knowledge under one idea by such early church fathers as Clement of Alexandria. Although it had the same name, this was very different from German eclecticism.
How is it possible to classify Gassendi, Bacon, and Locke together? Here one can realize the pitfalls of assigning one name to logical schools. For example, Gassendi did write a treatise attacking scholastic logic, Adversus Aristoteleos as he called it. This treatise was really attacking the self-referential syllogistic reasoning of dialectic, and often criticizes the Scotist philosopher Eustachius St. Paul, teacher of Descartes, and quotes Benedito Pereira, the anti-Platonic and anti-Scotist Aristotelian at the Collegio Romano. Gassendi dismissed Eustachius as Scholastic or Aristotelian, while he was developing his own version of the anti-Platonic logic of the sixteenth century that he reworked with his own recreation of Epicurean logic.
A further discussion of logic can be reduced to five points: 1) the use of rhetoric as a tool of persuasion by logicians; 2) the transformation of logic by anti-Platonic Aristotelian philosophers and their development of the question, De primo cognito?, 'What was the first thing thought?'; 3) this orientation of logic leads to the very specific criticism of the Neoplatonic myth of the prisca philosophiae, the 'first philosophers'; 4) the development of a technical vocabulary for natural philosophy that was a direct result of inductive logic: as myth and metaphor were rejected for biblical commentary, so Platonic myth and metaphor was to be shunned for inductive reasoning; 5) the hermeneutic of language for logic, which was then applied to the writings of logicians in the past and provided a tool for judging past thought. Thus the history of philosophy was born, and its midwife was logic.
Rhetoric and Logical Reasoning
The scholarship of Letizia Panizza and Heikki Micheli has made it quite clear that, as Micheli writes, "there is no justification for separating rhetoric from logic." The model of the correct logical proof changed dramatically when techniques of rhetoric were used. As Panizza explains, medieval philosophers "who learned their dialectic mainly from Boethius commentaries on Cicero and manuals of logic did not pay attention to Aristotle and Cicero on the close rapport of dialectic and rhetoric" (Cicero's De Oratore, a work only known after 1421). Panizza also explains that by the end of the fifteenth century, "Aristotle is held up as a model for an orator who wants to unite not only eloquence with philosophy in general, but rhetoric with dialectic."
She goes on to explain that logic was the instrument for philosophical thought, while rhetoric was the technique used to convince the reader. The philosophers adopted the persona of the orator, which was about the only technique used by Renaissance historians. By the time Zabarella (1532–1589) published De Methodis in 1578, rhetoric was being used to convince the reader of his method. Zabarella began each book of his treatises with a summary statement of method in which he declared his objectivity about his topic and his modesty towards knowledge, just as historians before him had done. After declaring his objectivity, he stated why his method of logic was superior to all others.
But the philosopher's use of the first person, in imitation of the speech of an orator, really developed in France with René Descartes's (1596–1650) Discourse on Method and Gassendi's persuasive voice in the Syntagma. In his work, Descartes declared the originality of his thoughts. He tended to assert the truth of his logical statements with rhetorically styled sincerity rather than engage in argument. Regius, a fellow philosopher, was so annoyed at the Cartesian use of persuasion rather than logic for proof that he wrote to Descartes, "any mad man can claim he is right." Descartes declared, "I think therefore I am." On the contrary, the first thing thought by Gassendi was not an a priori judgment; to him, thought had a history. He studied what past philosophers had thought, and he judged and critically examined the logic of the position. This led him to write a history of logic, the first comprehensive history up to that time.
Anti-Platonic Philosophers
Charles Schmitt wrote that Zabarella's logic set the stage for the logic used in the seventeenth century. Logic texts quoted Zabarella's attack on a priori reasoning and praised his logical method of setting out information not only in the seventeenth century but into the eighteenth. Johann Syrbius of Jena began his 1715 logic text with a critical history of the attack against a priori reasoning. He begins with a short historical discourse on the proposition that species originated in the mind, beginning with a quote from a commentary on Aristotle's De anima by the Portuguese Coimbra philosopher and Zabarella and ending by having linked the earlier traditions with the contemporary philosophy of John Locke and Robert Boyle. He also criticized Descartes, who believed that the species originated in the mind.
Neoplatonism
Not only was a priori reasoning rejected by specific philosophers, but the same anti-Platonic argument was used against the nonhistorical view that the prisci philosophiae or prisci sapientes could have known all of human knowledge without having learned it. For the Neoplatonists there was one truth that could be found in different forms in different religions around the world. This universal truth was proposed in the fifteenth century by Marsilio Ficino and was still of interest in the seventeenth to the Jesuit polymath Athanasius Kircher. Kircher's magnificently illustrated book of Noah's Ark, in which all of the knowledge known intuitively by early man is set out among the rooms, is a delightful visualization of universal knowledge.
There was an encyclopedia based on the other view. Zabarella said that as unlearned men, the prisci only knew what was in their nature. As the first thing thought was only hazily understood and had to be observed, identified, and then named, human civilization followed the same pattern. Initially humans knew nothing and had to understand the world through trial and error. A clever person appeared and made improvements, then others asked to become apprentices so that they could learn the logic of that person's way of working. Finally, all of this knowledge was written down. Adam, Moses, and Hermes Trimegistus are not part of this world: they all had only natural knowledge.
Just as there was not only one universal truth, there was not only one logical method for all disciplines. The greatest and most comprehensive history of disciplines was set out in 1708 in the Polyhistor by Georg Morhof (1639–1691). He articulated the difference between the disciplines as a logician articulates the difference between different sense impressions in inductive reasoning. Once the field of learning was identified, then the early and unclear beginnings of thought could be described and its history told as the history of the progress of the logic of that field of knowledge.
The Vocabulary of Natural Philosophy
If logic could control the organization of knowledge, it also dictated correct vocabulary. Research has shown that this hermeneutics of language was used as a weapon against Platonic philosophers. Perhaps no one was criticized for his vocabulary more than Paracelsus (c. 1493–1541), the innovative medical philosopher who developed a vocabulary for spells to use in medicinal cures. Medical doctors like the Swiss Thomas Erastus (1524–1583) attacked the Paracelsian language of spells for its attempt to be universal. Erastus said that no word is universal, but is particular to the civilization in which it is found. Spells and magic tried to unite heaven and earth into a chain of being that did not exist, Erastus complained. He asserted that there was a separation between the realms.
If natural philosophy and medical science were to improve, logic had to be used. Logic must order sense perceptions in such a way that what is known is recorded and what is unknown discovered. To do this, a precise vocabulary had to be devised. There was such interest in identifying the correct type of vocabulary for inductive reasoning and identifying Platonic or Scotist definitions that at the turn of the seventeenth century Goclenius's Lexicon was published, which set out the different types of words for different types of logic.
Application of Logic to the Philosophy of the Past
Not long after Zabarella's attack on the logic of prisci sapientes, the various types of logic of the various philosophers came under scrutiny. Anthony Grafton pointed out that Isaac Casaubon discovered that the Neoplatonic texts by Hermes Trismegistus were third-century forgeries. This discovery paved the way for a reassessment of Egyptian civilization. When the logic of earlier philosophers was identified, examined, and judged, an important change occurred: the critical characterization of the logic of past philosophers, the identification of philosophers not chronologically but by the success of their logic, changed the way people viewed past philosophy.
Pierre Gassendi wrote the first history of logic. His little-known work De Logicae Origine et Varietate, published in 1648 as a preface to the Syntagma, took the reader on an intellectual trip from the logic of Adam to the logic of Descartes. Adam, wrote Gassendi, did not have logic when he argued with the snake: "He was merely quibbling." He also argued that none of the patriarchs in the Bible were capable of logic either. Logic began with the Greeks and Zeno. Gassendi then criticized Plato's logic because it depended on a priori thinking and "was too much like theology." Although he admitted there was much to admire in Aristotle's logic, Gassendi wrote that it had been spoiled by his followers.
Gassendi admired the logic of the ancient philosopher Epicurus, based on inductive reasoning. Gassendi constructed a believable Epicurean logic in this text that appeared in student logic texts until the mid-eighteenth century. Jean le Clerc, friend of both Robert Boyle and John Locke, wrote perhaps the most widely used of these logic texts. From Epicurus, Gassendi passed over the Middle Ages, cramming one thousand years into two paragraphs, then began in the early modern period with Francis Bacon and the establishment of inductive reasoning. Bacon, wrote Gassendi, went the "heroic way." Gassendi made Bacon as the hero of contemporary thought. There is a great deal of rhetoric in this history of logic.
Finally, the complete triumph of logic as the history of logic came with the work of the German historian of philosophy Jacob Brucker (1696–1770). At Jena, Brucker was a student of Johan Jacob Syrbius, who had linked contemporary English inductive reasoning with the earlier logic of the Coimbra commentaries and Zabarella's De Methodis. In 1723, Brucker wrote a history of logic called Historia Philosophia Doctrinae de Ideis. In this work he attacked the prisca philosophiae in the person of Zoroaster. Following Gassendi, whose history of logic he knew, Brucker judged each philosopher by whether he used inductive reasoning. He praised Epicurus among the ancient philosophers and dismissed Renaissance philosophers like Valla and Vives, while praising John Locke and Robert Boyle.
Although the early modern period saw many breaks with past tradition, it did not usher in a new logic all at once. Rather, it was a period in conversation with past philosophy: sometimes it agreed, sometimes it disagreed, and sometimes the philosopher transformed his sources beyond recognition. As the De primo cognito? question was reworked by the anti-Platonic philosophers, the concept of intellectual (as opposed to chronological) progress developed in the sixteenth and seventeenth centuries. Nowhere can the concept of progress be seen more clearly than in the history of logic.
Bibliography
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Gassendi, Pierre. "De Logicae Origine et Varietate." In Opera Omnia, vol. 1, pp. 35–66. Leiden, 1658. Reprint, Stuttgart-Bad, 1994. The English translation, Pierre Gassendi's "Instutio Logica" (1658): A Critical Edition and Introduction by Howard Jones (Assen, 1981) does not include a translation of Gassendi's history of logic.
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——. "Vocabulary as a Critique of Knowledge: Zabarella and Keckermann—Erastus and Conring." In Philologie und Erkenntnis: Beiträge zu Begriff und Problem Frühneuzeitlicher "Philologie," edited by Ralph Häfner. Tübingen, 2002.
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—CONSTANCE BLACKWELL
