§26. A Chancellor and Bishop

The scientific challenge of the twelfth and thirteenth centuries was to com­bine the robust empiricism of the arts traditions with the new idea of scientia in works of Aristotle that began to appear at this time.

The idea of reaching beyond the limits of knowledge to find out new things was a mind-expanding novelty. Tradition sided with St. Augustine. “The mind is subject to a certain propensity to use the senses of the body, not for self-indulgence of a physical kind, but for the satisfaction of its own inquisi­tiveness.” He condemned the abuse:

This futile curiosity masquerades under the name of science and learning.... It is to satisfy this unhealthy curiosity that... men are led to investigate the secrets of nature, which are irrelevant to our lives, although such knowledge is of no value to them and they wish to gain it merely for the sake of knowing. It is curiosity, too, which causes men to turn to sorcery in the effort to obtain knowledge for the same perverted purpose.¹⁵

Posterior Analytics had been translated into Latin around 1140 but was slow to circulate due to its difficulty and lack of interest in its subject. The treatise provided a context for Grosseteste to unite the experimental empir­icism of the arts—then the best knowledge at Europe’s command—with the rationalism of the new natural philosophy. Grosseteste is early in a series of European thinkers fascinated by the idea of a mathematical universe created by a mathematician deity, a motif to be developed by Roger Bacon, John Dee, Galileo, Kepler, and Descartes.

Grosseteste’s departures from Aristotle arise from his understanding of God as infinite and creative. He exposes lingering polytheism and pantheism in Greek assumptions about divinity. No natural necessity imposes limits on God’s unconstrained freedom. Grosseteste also favored astrological and al­chemical ideas, objects of his first scientific passion. He criticizes Aristotle’s theory of discontinuous celestial and sublunar realms. The stars act on the earth in virtue of their elemental qualities, which requires them to be com­posed of the same stuff' as things on earth. Nature is one material everywhere, and action anywhere ripples everywhere. These points, which Grosseteste imbibed with his alchemy and astronomy, are incompatible with any reading of Aristotle’s natural philosophy, and opened a breech in Aristotelianism into which Ockham, Buridan, Oresme, Cusanus, and Bruno venture, to homoge­nize and mathematize nature.¹⁷

In his commentary, Grosseteste accepts Aristotle’s thought that the senses are the beginning of knowledge, and that even scientific demonstrations must pass through experience. No ideas are innate; one less sense would be one less science. The substance of things is hidden but he optimistically proposes that with diligence the veil will fall.

While accepting an Aristotelian natural philosophy, Grosseteste places the whole system between brackets and makes it respond to alien prepossessions. Christianity is one, alchemy another, and so is experimental inquiry. Grosseteste is the first medieval writer to deal with problems of ex­perimental verification, when he tries to apply Aristotle’s logic of demonstra­tion to experiments. He encountered the challenge of verification with the astrolabe, an instrument for predicting the positions of the sun and stars, determining local time, surveying, and casting horoscopes. Astrolabes were in use from the second century bce, and came to Europe from an Arabic source, reaching England in the eleventh century, where their use quickly spread. To adapt Arabic texts and star charts to the northern latitudes, which Grosseteste did, required competence with the astrolabe and the necessary calculations. A modern biographer writes that “so far as we know he was the first European who was able to command this whole field of knowledge with its growing bulk of Greek and Arabic texts, without needing to seek it in dis­tant parts of Europe.”¹⁹

The reasoning in this astronomical work was palpably different from the method of authorities practiced in the schools, not least in admitting of empirical refutation. He seems to have thought that the right explana­tion of Aristotle’s treatise on science could bring the evidence of experi­ence gathered in the arts into natural philosophy. Demonstration verifies conjectures on causation by deriving hypothetical consequences and testing them experimentally. He emphasizes the value of falsification in the search for true causes.

Experiments proceed in two phases: first, resolution from composite objects of sense to elements and principles, using experiments to sort out which elements and relations are common to the cause, then a deductive mo­ment called composition, in which the observed facts are demonstrated from the explanatory principle. We saw this method earlier (§6). Plato credited it to Hippocrates, and it reached a summit in Galen’s method of qualified ex­perience. Grosseteste’s explanation, unstably combined with an Aristotelian theory of demonstration, became variously known as the method of resolu­tion and composition, analysis and synthesis, or the regressus.

Grosseteste uses the word “experiment” much as we expect: a controlled procedure intended to verify a hypothesis. That is another idea he did not learn from Aristotle, whose theory of science enrolls experience but not ex­perimentation. Grosseteste’s inspiration may be Arab commentators, most likely al-Ghazali, who was paraphrasing Avicenna’s Logic. All three authors use the same example, predictably from medicine. Here is Grosseteste’s version:

Now when the senses several times apprehend two sensible objects, of which one is the cause of the other or in some other way related to it, and they do not apprehend the mediating relation itself, as, for example, when someone sees many times the eating of scammony accompanied by the dis­charge of red bile and he does not see that scammony attracts and draws out red bile, then from the frequent perception of these two visible things [the power of sense] begins to form a notion (estimare) of the third, invisible el­ement, that is, [in this case] that scammony is the cause that draws the red bile out. And on account of this notion (intentio estimata), formed many times and stored in the memory, and on account of the sensory perceptions (intentiones sensate) from which this notion is derived, the reason wakes up.

This passage is apparently his fullest statement on experimental logic, and there is nothing like it in earlier European tradition, so I want to examine it. A “power of sense” is said to form an estimare, an estimate of an unseen factor in the phenomena. It is this estimating, conjecturing power, interposed be­tween sense and concept, that devises a hypothesis. The terminology comes from Ibn Sina, who introduced the idea of inner sense and a new kind of sen­sible, the “intention,” perceived by the inner sense of estimation (wahm), not by the external senses. The estimative power, one of four inner senses along with imagination, memory, and the common sense, is a sub-intellectual fac­ulty that we share with all animals. It is an internal sense, a power of the sen­sitive soul additional to the external or special senses, with its own cognitive objects (maani, intentiones).

These intentions are most of our experience (tajriba), and include the objects of desire, benevolence, enmity, and undesirability. Even health can be an object of the estimative power and can flow from the physician’s in­tention to a patient. “True medical healing is that which occurs when the form of health, found in the soul and specifically in the wahm of the physi­cian, is transmitted directly to the patient and is the cause of his cure.” The unity of the “intention” group is sensed qualities that escape the perceptual capacity of the external senses because they are not essentially material.

It was appropriate for Grosseteste to locate the power of hypothesis in this estimative power, for in advance of experiments a hypothesis can only be invented, and one must not be troubled by an initial absence of reasons. Avicenna says that “estimation is the greatest judge in the animal, for it judges by way of an imaginative arousal without this being verified.” The estimative power is the source of the new idea, the hypothesis to explain the phenom­enon, doing what Aristotle asked of epagoge, but in an experimental setting. Instead of spontaneously educing the universal from uncontrolled experi­ence, this power “estimates” or conjectures qualities of an unseen cause, followed by an orchestrated test. In Avicenna as in Grosseteste, the conjec­ture is an intention of the estimative power, sensible, potentially sagacious, and not a fanciful product of the imagination.²²

It is difficult to think about experiments without practicing some, and Grosseteste was no armchair methodologist, being credited with having ini­tiated modern research in optics. He started with almost no knowledge of what had been achieved in antiquity, and began a tradition of experimental optics that became the point of departure for research down to the seven­teenth century. Grosseteste is the first medieval writer systematically to discuss mirrors, lenses, and the rainbow. His writings also contain influen­tial discussion of comets, tides, and heat, making extensive use of experi­mental reasoning, offering early examples of the regressus method, born of Grosseteste’s tormented effort to make Aristotelian scientific demonstration into a method of experimental discovery.²³

For instance, his problem in De calore solis is how the sun warms things. The phenomenon is stipulated as a fact and an effect. The first step of the method is resolution, decomposing the effect into three principles: a hot body, motion, and the collection of solar rays. The effect is not generated by the hot body, for there is no contact, nor by the sun’s motion, for the motion is circular and (he says) circular motion does not generate heat. So it has to be the concentration of rays. Then comes the moment of compositio, which uses the principle just educed from the effect to “explain” the effect. Grosseteste recounts a battery of experimental confirmations and falsifications to es­tablish his conclusion that solar rays become incorporated in the trans­parent medium of the air and communicate their energy as a vibration to the warmed body.²⁴

Aristotle expects experience to come to him bearing principles like a server at a banquet. To introduce deliberate modifications of experience is an im­portant innovation. That is what Grosseteste began, despite the compromises required by loyalty to syllogisms. He thought about nature as deeply as an­yone in Europe in this whole period, composing treatises on tides, rainbows, comets, and the sun. He understood the logic of experiments, which he ap­plied in his resolutio-compositio demonstrations, but he has little experience of experiment, which he readily confuses with what he reads in books. For instance, he says that at high tide seawater is hotter than at low, and ships draw more water than at low tide. It never occurred to him to test this.²⁵

In this respect his contemporary Albert the Great was perhaps the more sedulous empiricist. He questioned ancient lore on fishes when it conflicted with what he had “seen with his own eyes and heard with his own ears, dili­gently observing and inquiring from veteran fishermen of the sea and rivers.” Neo-Aristotelian scholars did not require Grosseteste’s Pythagorean enthu­siasm to take a new interest in empirical investigation, as Albert attests. His De mineralibus (ca. 1250) is written in awareness of compiling a new work and opening a new branch of scientia, because he found so few earlier works. He had heard that Aristotle wrote on the topic but could not find the work and considered Avicenna’s treatment unduly concise. Albert draws on what he learned from lapidarists, alchemists, pharmacists, and miners, and refers several times to personal experience in testing the powers of stones. “I became a wanderer, making long journeys to mining districts, so that I could learn by observation the nature of metals... this is the best and surest method of in­vestigation.” His fieldwork could be arduous. Among his observations is that eagles produce two eggs but only a single chick. “This is what we have learned by visiting the nest of a certain eagle for six years in a row,” observations that required being lowered down to the eyrie by a long rope.²⁶