The works Bacon produced during the 1240s differ on several aspects from the works and ideas he developed after returning to Oxford. In his early period of writing (1240s), he wrote on grammar (Summa grammatica), logic (Summa de sophismatibus et distinctionibus and Sumulae dialectics), and questions on several Aristotelian and pseudo-Aristotelian texts such as the Physics, Metaphysics, De causis, and the De sensu et sensato. These were probably the notes of his lectures, copied down much as he gave them in Paris.
The Summa grammatica was a systematic exposition of the principal points of syntax in the tradition of the Priscian commentaries. Bacon’s idea of the utmost significance of the speaker’s intention appeared already in this early text. He claimed that the speaker may distance himself from the proper grammatical rules in order to express some precise idea. In his early works on logic, Bacon developed his notion of imposition and his theory of equivocation, according to which a word which is applied to both an entity and a nonentity is the most extreme case of equivocation.
In this early period of his thought, Bacon held the agent intellect to be an inseparable part of the soul. He endowed it with the function of abstracting the incoming species from their material conditions, a function he would abandon later on. In some of his early works, he mentioned functioning innate exemplars, providing the soul with knowledge of universals, while in others, he referred to innate knowledge as vague and indistinct. In his mature works, these will be replaced with the talk of an innate capacity to acquire language, construct arguments, and recognize logical fallacies. Bacon objects to the idea that matter is one in number in all things, and holds to universal hylomorphism, according to which all things except God are composed of matter and form. Thus, Bacon will speak of the matter of both corporeal and spiritual beings, and hence of ‘‘spiritual matter.’’
At this point too, he affirmed that universals are extramental, and exist within particular, material objects. The soul does not make universality, so he believed, but finds it as a constituent of beings. He denied that the rational soul was the cause of universality, for even if it did not apprehend things they would still resemble one another. The universals in the mind, so he thought, are likenesses of external things, that is, they are the species of the ‘‘real’’ universals, those which are in particular, physical objects. The same position appears in his mature writings, especially in the Communia naturalium.
In his commentary on the De sensu Bacon suggested an arrangement of colors which was different from the one Aristotle proposed. Instead of a linear scale of colors from white to black, varying according to the amount of transparency in them, Bacon posited five distinct principal colors from which the other colors are produced by mixtures.
In the mature period of his work, Bacon abandoned the commentary literary style. He composed two general works, proposing and explaining his vision of the reform in Christian learning (the Opus majus and its two abridgements, the Opus minus and Opus tertium, and the Communia naturalium); two optical treaties (De speculis comburentibus and the De multiplicatione specierum), of which the latter presents not only his account of light and vision but of natural causation in general; one extended mathematical tract (Communia mathematica); and several works on language and semiotics (De signis, Grammatica Graeca, and the Compendium studii theologiae). Some of his writings (the Opus tertium and the compendium studii philosophiae) were devoted in part to social and political criticism. To this are added some small treaties on medicine and alchemy and of course, Bacon’s edition of the Secretum secretorum.
The Opus majus was to a great extent a plea for the study of the practical arts and sciences. Practical truth should prevail, according to Bacon, over theoretical truth. The end of speculative knowledge lies in its practical application. Accordingly, for each science he writes about,
Bacon adds a list of its possible uses. Thus, knowledge of foreign languages can foster the development of commerce as well as secure peace between nations and knowledge of alchemy can be used to prolong human lives. Optics can help shape a mirror in which one group of soldiers will appear as multiplied and thus terrify the enemy. Theology and moral philosophy are the most practical of them all, since they actively contribute to man’s salvation. These sciences should therefore be considered the summit of human knowledge and all the other disciplines considered their aides.
Bacon maintained that a theologian must know the things of this world if he is to know the sacred text. This conviction stands at the heart of his proposal for revising the curriculum in the universities. He explained the corruption of studies in his time by the practice of young theologians to preach and teach without first undergoing a full liberal arts training. Bacon wanted theologians to be versed not only in the liberal arts but also in the seven practical sciences, including perspective, astronomy, the science of weights, medicine, experimental science, alchemy, and agriculture. Without knowing those subjects, so he argued, the theologians would not be able to understand the literal meaning of Scripture, and consequently, incapable of understanding their spiritual meaning as well.
The method of inquiry to be used while pursuing these sciences should be, according to Bacon, ‘‘experimental science.’’ Logical arguments alone, so Bacon argues, cannot provide the certitude our mind requires. If we wish to attain certitude, we must actively experience the things of the world with out external senses. He listed three tasks for experimental science: to investigate the conclusions of the speculative sciences; to construct new instruments and gather new data; and to supply predications. While some modern scholars have championed Bacon as an experimentalist in the sense of Francis Bacon (15611626) and as a mind far beyond his era, others saw him as a pragmatist or at best an empiricist in the Aristotelian sense. Recently, Jeremiah Hackett arrived at the conclusion that Bacon’s experimentum was not simply a repetition of Aristotle’s empiria, but in fact a critique of pure syllogistic reasoning. Hackett adds that the Opus majus provides strong evidence for actual experimental work with instruments in which Bacon was involved, and discerns a small but definite influence of Bacon on his namesake, Francis.
A conspicuous feature of Bacon’s advocacy for a new order of studies has been his praise of mathematics as essential to the study of all other sciences. Although his name is not subscribed under any significant mathematical achievement, he grasped better than most of his contemporaries the fecundity of mathematics as a principle of scientific explanations, and its ability to provide certainty in science. When combined with experimental science, the science of math guarantees full truth free from error or doubt.
An instance of how mathematics can be applied to a natural science discipline is the science of astrology. It studies the effects of the heavenly bodies on natural events and human characteristics, and can be used for general predication concerning human behavior. Bacon thought that the condemnation of astrology by many Christian authorities was harmful and impeded the efforts to convert unbelievers, yet qualified that astrological predications are not infallible.
Bacon’s major later work on Physics was the De multiplicatione specierum. In this work, he describes the most fundamental mechanism ofnatural causation, namely the propagation of species. Although the term had a rather large circulation in the thirteenth-century philosophical texts, Bacon had given it a systematic treatment to be found nowhere else. He defined a species as ‘‘the force or power by which any object acts on its surroundings,’’ and posited it as efficient not only on the sensory level but within natural and intellectual processes as well. A species, Bacon contends, is produced by every active nature; the list ofactive natures includes not only color and light, smell and most sensible accidental qualities, but also universals and substances. A species resembles its agent in ‘‘nature, specific essence and operation’’ and belongs to the same category as its agent. Thus, the species of substance is substance, the species of accident is an accident, and the species of a composite is composite. Bacon established the principle that a species is brought forth out of the potentiality of the matter of the recipient and through it an agent renders its surrounding similar to itself.
The action of species is of a natural character, which is uniform and necessary. Neither species nor their agents can exert will or deliberation; neither can designate one kind of species to inanimate objects, another to senses and yet a third one to intellects. Therefore, there is always only one kind of species being produced, and the variety of effects is due to the variety of recipients. Bacon emphasized the material and natural existence of species, in both medium and senses. There is no ‘‘spiritual being’’ in the medium as was taught by other scholastic philosophers. For Bacon, universal causation is corporeal and material, and matter itself in not just pure potentiality but is positive in itself.
Bacon was more of a theorist of science than an inventor. His most notable scientific achievement was the initiation of the tradition of Perspectiva in the Latin world.
He was a very competent reader and transmitter of the fruits of Arab scholarship, and especially of Alhacen (935-c.1039). He adopted Alhacen’s principle of emanation from each point on the object’s surface, and argued that the vision-producing rays are only those that are perpendicular to the eye. He successfully communicated the geometrical principles of reflection in mirrors; the precept of equality of the angels in incidence and reflection; and the rules governing the location, size, and direction of images in different kinds of mirrors. The phenomena of refraction was dealt with successfully all the same, and Bacon established the principles of refraction at interfaces of various shapes and various media, all accompanied by geometrical diagrams. In the De speculis comburenibus, he presented a minute treatment of the phenomena of pinhole images. He supplied a geometrical analysis of the eye, which would become a central feature of European theories of vision for many centuries. He then sketched the psychological processes involved in vision.
According to Bacon, sight can perceive 22 visible qualities among which are light, color, remoteness, position, corporeity, shape, size, continuity, number, and motion. Of these, only light and color are perceived directly, since they alone produce species, while the other visual qualities are deduced from the way the species of light and color are arranged on the surface of the eye, an arrangement which accurately reflects the original proportions within the issuing object. In deducing visual information, both humans and animals employ a kind of syllogism which resembles reasoning. Bacon ascribed complex cognitive capacities to animals; he adduced that spiders spinning their webs and monkeys taking revenge on people who have hurt them are examples of animals’ ability to learn from experience and to plan their actions accordingly.
Bacon describes the brain as divided into three chambers. The first chamber he calls phantasia and says it houses the common sense and imagination. Upon receiving the species, the common sense first makes judgments concerning each sense separately, discerning the distinctive kind of information supplied by the proper senses. The species are then retained in the imagination. In the rear chamber of the brain, the estimative faculty receives the species of the substantial nature of things, and memory retains them. The species retained in both phantasia and memory are multiplied all the way to the highest faculty of the sensitive soul, located in the middle cell of the brain: cogitation. The faculty of cogitation is the one responsible for the syllogistic mode of cognition, and serves as the link between the sensitive and the rational soul in men.
At this point, Bacon detached the agent intellect from the soul and identified it with God. He considered that according to Aristotle the agent had to be substantially other than the patient and therefore the potential intellect and the active one must be set apart. He then divided the rational soul in two: the speculative intellect and the practical one, which he recognized as the will. He designated the speculative part to the speculative sciences, yet ascribed rationality only to the practical intellect, dealing with the practical sciences, because it alone employs deliberation and freedom of choice. In his moral philosophy he relied heavily on Seneca (c. 4 BCE-CE 65) and strove to make his ideas known.
No cognitive act, Bacon stipulated, can occur without a due representation of the matter of the thing cognized. Bacon held to the view that all aspects of an object must be a part of its representation - the material properties as well as the formal ones. Accordingly, he insisted that a species represents the whole composite of form and matter. A composite species, according to Bacon, not only provides the most faithful representation of its agent but is also more readily and quickly grasped by the intellect. He expressed the same view in his theory of signs. The word, so Bacon declares, does not represent only the form or essence of the named thing; but rather signifies the composite of matter and form as a whole. Against Averroes (1126-1198), who argued that a word represents the form alone since the form is more worthy than matter, Bacon answered that a composite has whatever is of worth in a form and beyond this the worth of matter. This conception of representation is tightly linked with his view of matter as inherently positive and as an important factor in human life. His stress on the importance of the practical sciences is but another expression of the same position.
In his mature phase of thought Bacon developed more fully his ideas on language and the imposition of words. He presented an original classification of signs, in which one class included natural signs, representing their significates by concomitance, inference, and consequence, by likeness or in the manner of cause and effect. The other class comprised of signs given by a soul, which could be given either by employing one’s free will or naturally, as if by an instinct.
Words are, according to Bacon, signs given by soul and more specifically by the intellective soul acting rationally out of its own free will. Words differ from natural signs in that no essential linkage exists between them and their significates; they differ from signs given by soul naturally, in that they are based upon pure conception and arise from cognitive and rational processes involving knowledge, reflection, deliberation, and choice. The thing to which a voice is attached depends entirely on the speaker’s intent. Since in most acts of speech we intend to name extramental objects or events, Bacon argues that this external thing is what the word signifies, and not, as Aristotle and Boethius (c. 480-524/525) claimed, the image of the thing within the mind. This point is exemplified in the De signis, where Bacon argues that, when one says ‘‘Socrates runs’’ one does not intend to say that the species of Socrates is running.
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