EILEEN F. SERENE

ROBERT GROSSETESTE ON INDUCTION AND

DEMONSTRATIVE SCIENCE

Robert Grosseteste's commentary on Aristotle's Posterior Analytics is the earliest complete medieval Latin commentary on this work known today, t Its date of composition remains somewhat uncertain, but the best-supported estimates place it around 1220. 2 The commentary, which is based on the vulgate translation made by James of Venice in the second quarter of the twelfth century, appears in at least twenty-two extant manuscripts and in eight Renaissance editions) This commentary interests students of medieval philosophy and science for a variety of reasons. Although it was only the first of many medieval commentaries on the difficult work whose ideal of scien- tific demonstration apparently enchanted natural philosophers for centuries, Grosseteste's was also one of the most widely circulated commentaries on the Posterior Analytics. 4 So it is natural to assume that it may have exercised both an early and an enduring influence on the reception and understanding of this text. Since Grosseteste was the first teacher of the Oxford Franciscans at Merton College, it is possible that his views on Aristotelian science exercised a particular influence on the school which was to include such leading natural philosophers as Roger Bacon, Walter Burley, William Heytes- bury, and Thomas Bradwardine. 5 Finally, Grosseteste's commentary contains acute critical discussions of Aristotle's text. While Grosseteste primarily en- gages in literal exposition, he does more than paraphrase and implicitly endorse Aristotle's views; I believe that at several points he revises the Stagirite's theory of scientific demonstration. Indeed, it Would be surprising for Grosseteste not to revise the theory from the point of view of his own Neoplatonic, Augustinian commitments in epistemology and metaphysics.

Current appreciation of the significance of Grosseteste's commentary is due to the work of A. C. Crombie, whose captivating book entitled Robert Grosseteste and the Origins of Experimental Science 1100-1700 (Oxford: 1953) accords credit to Grosseteste for influential advances in the methodology of science and in experimental practice. Crombie's case for the originality and importance of Grosseteste's methodology of science hinges largely on an interpretation of his view of induction which ascribes to our

Synthese 40 (1979) 97-115. 0039-7857/79/0401-0097 $01.90. Copyright 1979 by D. Reidel Publishing Co., Dordrecht, Holland, and Boston, U.S.A.

98 EILEEN F. SERENE

thirteenth century author the following rather modern line of reasoning. 6 Scientific reasoning depends for its premises on universal causal principles which we grasp only through intuitive induction; but since intuitive induction of universal causal principles rests on a 'logical leap', no scientific explanation can ever be fuUy confirmed. The scientist's function, then, is to attempt to falsify at least some of the plausible possible explanations of phenomena. Since more than one hypothesis might survive attempts at falsification, and since intuitive induction is epistemologically problematic, the scientist should regard his reasoning as a source of sufficient explanations of phenomena rather than as unique accounts of their necessary causes. This interpretation depicts Grosseteste as a skeptic regarding the certainty available to the natural philosopher. While Crombie notes that this skepticism applies properly only to the realm of reason alone, that is, to reason unaided by divine illtunination, he thinks that it led to a shift from the Aristotelian goal of demonstra- tive certainty to a new goal of 'probable' explanations. Thus, in the alchemy of Crombie's interpretation, Grosseteste [s transmuted from the modified Aristotelian he appears to be, into a medieval Popperian. 7

Unfortunately, my reading of the text calls into question much of the evidence which Crombie adduces to support his intriguing interpretation of Grosseteste's ideas about induction, and it suggests an interpretation which is rather different in emphasis. In my judgment, the role divine illumination plays in Grosseteste's account of demonstrative reasoning actually under- mines skepticism with respect to scientific certainty. A full discussion of the philosophical issues and historical questions connected with Crombie's study of Grosseteste and his influence far exceeds the scope of a single paper; here I shall concentrate on epistemological issues arising in Crombie's account of the nature and significance of the view of induction which Grosseteste takes in his commentary. In Section I, I shall summarize what I understand to comprise the main evidence for Crombie's conclusions regarding Grosseteste's view of induction. In Section II, I shall discuss my doubts concerning the adequacy of this evidence. In the final section, I shall introduce some features of an alternative interpretation of Grosseteste's view of induction and demon- strative science.

I

I believe that it will be helpful to preface our examination of Crombie's conclusions and the reasoning which supports them with a brief review of

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som~ salient features of the theory of demonstrative science presented in the Posterior Analytics. Since this theory is notorious for its obscurity, I shall simply identify the features of the theory which are directly relevant to understanding and assessing Crombie's claims, without discussing their in- terpretation and rationale in detail, s According to Aristotle, the aim of natural philosophy is the acquisition of scientific or demonstrative knowledge (episteme in Greek, scientia in Latin) of phenomena. 9 This knowledge is expressed in, or produced by, an axiomatized deductive system of syllogisms which meet a number of special requirements. 1 o Full-scale scientia has as its object a 'reasoned fact' which is the conclusion of a first figure syllogism in barbara form whose premises are true, necessary, universal, immediate, and appropriate to the genus and species under consideration, i t The major premise must be universal with respect to the appropriate genus or species, and the middle term must be a proximate cause of what is explained in the conclusion.~ 2 In addition, in a paradigmatic demonstrative syllogism the cause must be simultaneous with its effect. 13 A syllogism which meets these requirements will be capable of showing the existence of, or reason for, a certain fact, or capable of elucidating what a certain kind of thing is; in other words, the syllogism will display why the phenomenon contained or 'saved' in the conclusion is necessarily so, by specifying its uniquely necessitating causes.14 Aristotle also specifies an intensional requirement for such a syllo- gism to produce scientia in a knower: that person must realize that the syllogism meets all these special requirements, and thus realize that it explains why the conclusion is so, not just that it is so. ~ s So while the logical structure of a demonstrative syllogism is simple, the additional requirements seem to limit severely the number of barbara syllogisms which will count as genuinely demonstrative. 16 In fact, it is far from clear that any of Aristotle's own examples fully satisfy these requirements. 1 ?

While Aristotle sees demonstrative syllogisms as at least the most per- spicuous way to present explanations of some sorts of phenomena, he argues in detail that the primary premises of demonstrations are not themselves demonstrable, is Thus successful demonstrative reasoning requires correct apprehension of indemonstrable premises. Unfortunately, Aristotle's account of the correct apprehension of indemonstrable premises is laconic; what he says is that experience (empeiria), induction (epagoge), and intuition (nous) contribute to the grasp of primary premises. 19 And he recommends the method of division as an algorithm for formulating the definition of a genus

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and its species once one has a rough idea of what belongs to the genus. 2 That is, one constructs definitions per genus et differentiam by organizing the members of a genus according to their similarities and differences. Aristotle thinks that the middle terms of demonstrative syllogisms are definitions, that these definitions are often discovered simultaneously with the phenomena to be 'saved', and that the major premises of syllogisms and first principles of sciences must be discerned by further reflection on the subject. 21 It is traditional to note at this point that Aristotle's interest here lies not in developing an account of the art of discovery of premises for demonstrative syllogisms, but rather in specifying the appropriate way to present the structure of a science once its primary premises and middle terms have been recognized.

It is far from obvious what a full Aristotelian account of the correct apprehension of primary premises would contain, and there is scant consensus regarding the appropriate reconstruction of the few remarks Aristotle makes on induction and its relationship to nous. Interpretations of Aristotle's view of the nature and limitations of induction rest primarily on alternative readings of Book II, chapter 19 of the Posterior Analytics. The orthodox interpretation holds that induction is a necessary but not a sufficient con- dition for apprehension of first principles, while the empiricist interpretation holds that induction is a sufficient condition. According to the orthodox reading of the last chapter of the Posterior Analytics, Aristotle believes that nous is an additional necessary condition for the apprehension of first principles; Jonathan Barnes summarizes this view vividly:

.. in B 19 Aristotle recognized, at least tacitly, the notorious frailty of induction: [simple or enumerativeT induction, according to B 19, cannot by itself get us to the principles; there is a chasm which induction will not leap - we must fly over it on the back of intuition. The principles, in short, are apprehended by induction plus intuition, or by 'intuitive induction'. 22

But Barnes himself advocates the alternative, empiricist view which holds that in this chapter Aristotle introduces nous to characterize the dispositional state of the person who has successfully completed an induction, not to posit an additional means of acquiring knowledge. A telling point in favour of this interpretation is the characterization of nous as a state (hexis) at 10065-14. According to this view, then, Aristotle does not envision a chasm over which induction cannot leap, and so his account need not posit a philosophical

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problem of induction which can be met only by positing a mysterious act of nous. Barnes thinks that "nous, the state or disposition, stands to induction as understanding (episteme) stands to demonstration. Understanding is not a means of acquiring knowledge. Nor, then, is nous.'23

The second interpretation tends to exonerate Aristotle from the charge that he fails to explain how one discovers primary premises. But it still leaves open the question how one recognizes that an apprehension of a primary premise is correct. What are the criteria for being certain that one is in a state o f nous with respect to a concept or principle? To my knowledg_e, Aristotle does not raise this skeptical question. He assumes that we do have demonstra- tive knowledge, and so must be in a state of nous with respect to some primary premises. While he recognizes that there may sometimes be difficulty in deciding whether a syllogism is truly demonstrative, he does not treat this

" "~4 objection as a serious eplstemologlcal problem.-

Does Grosseteste's treatment of induction and nous align itself with either the orthodox or the empiricist view, or does he take another line of interpre- tation? I think that Crombie's reading of Grosseteste rests on the assump- tion that Grosseteste accepts the orthodox view, since he writes:

But Grosseteste knew that there was a logical hiatus between asserting a formal definition, or generalization stating the regularity actually observed, and asserting a theory stating a universal and causal connexion. To leap this gap in the logical process of induction he envisaged an act of intuition or scientific imagination, corresponding to Aristotle's nous, by which the mind reflecting on the classification of facts produced by induction suddenly grasped a universal or principle or theory explaining the connexion between them. 2 s

In a footnote, Crombie emphasizes that this remark applies only to the problem of intuitive induction, that is, the induction of universal causal principles, and not to the problem of enumerative induction. 2 6 In enumera- tive or simple induction, one formulates a generalization about a genus or species on the basis of a sample which is less than exhaustive; for example, by enumerative induction one asserts universally that humans are rational, with- out observing each member of the species. In Crombie's view, Grosseteste recognizes this distinction between intuitive and emunerative induction, be- lieves that each involves at least a prima facie leap over a logical gap, and proposes separate justifications for each sort of induction.

The justification of enumerative induction rests on acceptance of a principle o f the uniformity of nature which holds that causes, including the

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formal cause of each species, always have the same effect unless there is some external impediment to their normal operation. If a classification based on observations 1 through n suggests that rationality belongs to being human, if nature is uniform, all humans are rational. Of course, the principle of uniformity cannot contribute to the justification of enumerative induction unless it has a basis apart from observed regularity alone. Crombie supposes that Grosseteste considers this principle to be a fundamental, self-evident truth;27 but he also supposes that the principle of uniformity alone cannot justify, or even explain, the assertion of universal causal connections, z8 The reason Crombie suggests for this, in the passage I quote, seems to be that causal connections are in principle not directly observable. Thus Crombie concludes that the apprehension of a causal principle requires a special act of intuition, corresponding to Aristotle's nous, in addition to observation and classification of data, and in addition to whatever generalizations can be made the help of the principle of uniformity.

Crombie ascribes this diagnosis of the problem of induction to Grosseteste, then reconstructs what he takes to be Grosseteste's response to the problem of intuitive induction. It seems to me that this reconstruction involves making a firm distinction between Grosseteste's theoretical response and his practical response. On the theoretical side, Grosseteste recognizes that all certainty with respect to necessary truths depends on divine illumination; 29 hence the ultimate justification for the reliability of causal explanations would be divine illumination. But on the practical side, Crombie suggests that Grosseteste provides a treatment of causal explanations which in effect ignores any role played by divine illumination. It is his practical response to the problem of intuitive induction which Crombie identifies as Grosseteste's leading contri- bution to scientific methodology and the rise of experimentation in science. And it is this part of the interpretation which Crombie supports in detail.

In Crombie's interpretation, Grosseteste's practical response to the prob- lem of intuitive induction rests on the recognition that for any phenomenon to be explained, there will be a plurality of possible causes. To support this claim, Crombie quotes from Book II, chapter 5 of the commentary:

Can the cause be reached from knowledge of the effect with the same certainty as the effect can be shown to follow from its cause? Is it possible for one effect to have many causes*. If one determinate cause cannot be reached from the effect, since there is no effect which has not some cause, it follows that an effect, when it has one cause, may have another, and so that there may be several causes of it. 30

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In the light of this recognition, the interpretation continues, Grosseteste advocates the following procedure for selecting the best causal explanation from the plurality of possible ones. First the scientist should attempt to falsify each principle by seeing if it entails impossible or absurd consequences. A theory which survives this falsification procedure constitutes a sufficient explanation of the phenomenon under consideration; but since typically more than one hypothesis will remain unscathed, none can claim to be the unique cause which necessitates the phenomenon. At that stage the scientist should rely on the assumption that nature operates simply and efficiently, and on that basis select the most appropriate hypothesis. 3

Grosseteste's use of an example drawn from Avicenna's Canon of Medicine illustrates his practical procedure for establishing scientific hypotheses and his concern for experimental falsification, in Crombie's opinion. The example occurs in the context of Grosseteste's discussion in Book I, chapter 18 of the relationship between knowledge and sense perception. While Grosseteste agrees with Aristotle that we typically abstract universal concepts from repeated perception of singulars, he denies that this is the only way in which knowledge can be obtained; his reason for this denial is that angels and other incorporeal intellects can know without sense perception. After making this general point, Grosseteste introduces Avicenna's example of how one grasps the universal principle that ingestion of the plant scammony causes the discharge of the humour red bile from the body. Grosseteste says that when we repeatedly observe that the eating of scammony is conjoined with the discharge of red bile, we form an aestimatio that the scammony causes the discharge. 32 Next our reason questions whether this aestimatio corresponds with reality. To answer this question, Grosseteste and Avicemaa say, we should make more observations under controlled conditions where we have tried to exclude other factors, besides the ingestion of scammony, which could be responsible for the effect. According to Crombie, Grosset~'s use of this example shows that he makes a special place for causal hypotheses,'~ and requires that they be tested under controlled conditions before they are accepted as causal principles. 33

As I understand Crombie's suggestions, they include four controversial claims about Grosseteste's view of the nature and limits of induction.

(1) Grosseteste's understanding of nous corresponds to the orthodox interpretation of the last chapter of the Posterior Analytics, but somehow divine illumination plays the role of nous.

104 EILEEN F. SERENE

(2) Grosseteste distinguishes between the problem of enumerative induc- tion and the problem of intuitive induction.

(3) Grosseteste's response to the problem of intuitive induction is to recognize that, given the plurality of possible causes of any effect, and given the unavailability of certainty in the absence of divine illumination, the natural philosopher can hope to find only good sufficient reasons for phenom- ena, and not their uniquely necessitating causes.

(4) Grosseteste's rejection of the Aristotelian quest for necessary reasons and his emphasis on experimental falsification were significant for the rise of experimental science.

If these claims are all tree, they constitute a strong case for thinking that Grosseteste both endorses and transforms Aristotle's theory of science. In a sense he endorses it by accepting what the orthodox opinion takes to be the explanation of how induction enables us to grasp true first premises, that is with the additional help of an act of nous, or its counterpart, divine illumin- ation. And Grosseteste transforms the theory by rejecting day-to-day reliance on divine illumination, and thereby rejecting Aristotle's official goal of achieving certain knowledge of a unique explanation for each phe- nomenon. 34 Hence for all practical purposes the scientist's job was to observe phenomena carefully and repeatedly, to construct possible hypotheses, and to attempt to disconfirm the worst of them.

II

It strikes me as thoroughly plausible that Grosseteste's life-work and even the material in his commentary in fact contributed to the rise of what we now take to be scientific reflection and experimentation. Grosseteste seems to have been the first person in the Latin West to have made much sense out o f the theory of demonstrative science in the Posterior Analytics, and his commentary elucidates the structure of the theory in a clever and clear fashion.3 s However, I have doubts about Crombie's account of the possible epistemological grounds for this influence, and accordingly I must question each of the four theses I have just formulated. I believe that these theses incorporate Crombie's views; but in any case it is their claims which I will discuss.

The first thesis asserts that Grosseteste follows the orthodox interpretation

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of nous, but somehow substitutes divine illumination for nous. This thesis raises a question which I consider central to a correct interpretation of Grosseteste's version of Aristotle's theory of science, the question of his view of the nature and role of divine illumination. It is hard to settle this question on the basis of the text of the commentary alone, however, since Grosseteste seems to append the doctrine to Aristotle's epistemology without fully explaining its ramifications, Since divine illumination sometimes serves as a poetic image or Christian talisman in medieval texts, rather than as a general account of human knowledge, it is easy to see how Crombie could suppose that Grosseteste introduces this idea only to relegate it to the realm

of irrelevance. But I think that one should be skeptical of such a surmise, for reasons which I will discuss in the next section. But regardless of whether the interpretation of divine illumination I shall suggest is persuasive, it is clear that this first thesis requires revision. Since the orthodox interpretation of nous and its relationship to induction strikes me as less plausible than the empiricist interpretation, I am happy to point out that Grosseteste could not have accepted it. In the orthodox interpretation, nous is characterized as part of the knower's evidential basis for induction, rather than as the state he achieves when he completes an inductive inference. But if Crombie is correct in thinking that divine illumination is a counterpart to nous, as I believe he is, then Grosseteste cannot follow the orthodox line. He describes complete knowledge as an irradiation of the knower by the superior light; 36 this irradiation can hardly be an activity or leap of the knower, but must be a state of the knower.

The second thesis asserts that Grosseteste distinguishes between intuitive and enumerative induction; the point of this distinction is to suggest that the former problem raises more serious epistemological issues than the latter. It seems to me that if Grosseteste does make this modern distinction, and denies that enumerative induction is as problematic as intuitive induction, that his view differs markedly fom Aristotle's. It is true that Aristotle and Grosseteste portray the process of grasping the formal cause or definition of a genus or species as relatively straightforward. 37 Grosseteste explicitly mentions that the method of division presupposes that we can accurately discriminate between essential and accidental properties of substances, but he does not question our ability to do so. 3 s So it is reasonable to conclude that Grosse- teste has no deep epistemological qualms about enumerative induction. How-

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ever, I fail to see that either Aristotle or Grosseteste distinguishes in principle between enumerative and intuitive induction. 39 Commentators have puzzled over the fact that the examples in Aristotle's discussion of induction and nous in the last chapter of the Posterior Analytics appear to deal with concept- formation rather than the apprehension of propositional principles. The most direct explanation of this difficulty I can see is to admit that Aristotle does not see a sharp or epistemologicaUy significant distinction between induction of a formal cause and induction of other explanatory causal principles. Perhaps this is a mistake or oversight on Aristotle's part; but any less direct explana- tion requires strong support.

There is ample reason to doubt that Grosseteste diverges dramatically from Aristotle in distinguishing a separate and severe problem connected with so-called intuitive induction of causal principles. I have found no texts which clearly require this interpretation. And there are many texts which show that Grosseteste follows Aristotle in considering definitions as the paradigm for the explanatory principles of science. He even enhances this special regard for definitions in two ways. He suggests, for reasons which I will not expound here, that a demonstrative syllogism be regarded as a composite definition of a phenomenon, one which accounts for both its formal and other causes. 40 Elsewhere, Grosseteste indicates that complete knowledge of the formal cause of a thing is identical to knowledge of the exemplar cause of that thing in the mind of God. 41 I do not see that Grosseteste's reliance on definitions as the paradigm for explanatory principles of phenomena rests on skepticism regarding the apprehension of correct causal principles apart from formal causes. Nor do I see why Grosseteste should suppose that divine illumination is more crucial in intuitive induction than in enumerative induc- tion, since his characterization of complete knowledge involves direct ac- quaintance with an exemplar cause, not a grasp of the principles of efficient causation; and complete knowledge requires full divine illumination.

The third thesis asserts that Grosseteste's response to the problem of intuitive induction amounts to a skeptical abandonment of the search for uniquely necessitating reasons for phenomena. Since this thesis rests on a distinction which I find dubious, I ought to reiterate my understanding of it. I shall continue to assume that the 'problem of intuitive induction' refers primarily to the fact that efficient causes which might constitute necessary connections between events are in principle not directly observable. Regard- less of whether this assumption corresponds to Crombie's intentions, and

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regardless of whether Grosseteste considers induction of principles of effic-

ient causation distinct from other instances of induction, the question of how

Grosseteste views the formulation of premises specifying efficient causes is

one of considerable interest. But since I am not convinced that Grosseteste's

views on the matter of discerning efficient causes differ markedly from his ideas on how to discern formal causes or definitions in general, I shall

concentrate here on some negative points. Against the background of various other assumptions, Crombie thinks that

Grosseteste's recognition of the plurality of possible causes of an effect leads

him to reject the Aristotelian goal of finding the uniquely necessitating causes

of phenomena. Aristotle himself has difficulty settling on a full account of

conjoint causal explanation, and so it is possible that Grosseteste inherits

some of his troubles. 42 But I do not think that one is forced to this

concession on the basis of the evidence Crombie adduces. The relevant

passage is this:

Can the cause be reached from knowledge of the effect with the same certainty as the effect can be shown to follow from its cause? Is it possible for one effect to have many causes? If one determinate cause cannot be reached from the effect, since there is no effect which has not some cause, it follows that an effect, when it has one cause, may have another, and so that there may be several causes of itJ 3

I do not fully understand Grosseteste's position on the general question of

conjoint explanations, but I think that this passage cannot be construed as a

metaphysical commitment on his part to the existence of a plurality of

possible causes of a particular effect. The quoted passage occurs where

Grosseteste is only paraphrasing Aristotle; the words preceding it are, "For in

the first place he inquires . . . . ,,44 And at this point Aristotle is raising an

aporia, and pointing out the line of reasoning which would lead to an affirmation of some sort of doctrine of a plurality of possible causes. But

Aristotle himself shortly gives a negative answer to the question he raises,

when he asserts that for explanations of the properties of the same sort of

individuals, there can be only one cause. 4s We can be confident that

Grosseteste does accept this po in t - that if a particular kind of effect is

demonstratively known, the middle term and the effect must reciprocate - because in his discussion of it he raises and resolves several dubitanda. Grosseteste points out, for example, that this assertion involves an assump-

tion about the organization and regularity of nature; it is not merely a point about demonstrative science. 46

108 EILEEN F. SERENE

But perhaps what Crombie means to assert is that there is a plurality of possible causes in the sense that the investigator has numerous epistemic alternatives available as he seeks to explain a phenomenon. He then would test his hypotheses to see which were untenable. Grosseteste surely would accept, as would Aristotle, the likelihood that a scientist would posit causal principles which later required revision. But Grosseteste does not always emphasize the importance of falsification through controlled experimenta- tion, as he does in the scammony example. Grosseteste's amplification of Aristotle's explanation why some animals have horns typifies his approach toward revising causal principles in the light of counter-evidence, a 7 First he considers the following principles:

(1) (2)

Having horns is not having teeth in the upper jaw. The cause of having horns is not having teeth in both jaws.

Apparently Grosseteste thinks of (1) as a statement of a formal cause, i.e. of what it is to have horns, and thinks of (2) as a statement of a material and an efficient cause, since the hard matter which would have become teeth becomes horns instead. But then he reflects that camels and female deer might be counterexamples, since he believes that they have only one row of teeth and yet have no horns. Grosseteste meets this problem by recognizing that these animals have other means of protection, and so he builds this proviso into his initial definition of 'having horns'. Thus he can argue:

(1)

(2)

All animals which lack one row of teeth and also lack other means of protection have horns. Goats lack one row of teeth and also lack other means of protection. Therefore, goats have horns.

While Grosseteste' advocacy of the revision of defective premises may be reassuring to anyone who thinks of the Middle Ages as a blot in the history of experimental science, it is not clear that it bears any special epistemological significance. In the light of reflection on or observation of the animal kingdom, Grosseteste revises the middle term of his syllogism. Since this involves a change in the statement of the formal cause as well as that of the material and efficient cause, I do not see that it pertains uniquely to what I assume Crombie means by the problem of intuitive induction. It certainly

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does not illustrate Crombie's supposition that there may be a plurality of epistemic alternatives for the investigator which all survive falsification.

Since the sense in which Grosseteste recognizes a plurality of possible causes of phenomena, i.e. in the sense of epistemic alternatives, does not in and of itself lead to skepticism with respect to the attainment of truly demonstrative syllogisms, the weight of the third thesis must depend on the assumption that divine illumination is not forthcoming, or cannot be ex- pected to be forthcoming. I shall simply note here that if, contrary to Crombie's assumption, Grosseteste believes that divine illumination is avail- able and reliable, there is no reason to infer that he abandons the quest for locating uniquely necessitating reasons for phenomena. Indeed, if complete knowledge is associated with the notion of divine illumination and direct acquaintance with the exemplar causes in the divine mind, Grosseteste has reason to advocate the pursuit of scientia with religious fervor.

Thus, part of the fourth thesis, that Grosseteste's work~was historically conducive to the rise of experimental science, may well be true, even if we do not follow Crombie's analysis of the epistemological grounds for this effect. But it seems to me that Grosseteste's use of Avicenna's scammony example does not necessarily show that he was aware of its special experimental implications. Since in the context its main point is to show how knowledge comes from sense perception, and since the example is not original to Grosseteste, we must at least question how seriously he takes its interesting features. I have found no evidence elsewhere in his commentary to suggest that Grosseteste takes controlled experimentation to be a necessary condition for the formulation of a universal causal principle, as distinct from an aestimatio or hypothesis. 48 Grosseteste simply uses Aristotle's elusive vocab- ulary of seeing or grasping what the middle term is. And Grosseteste himself defends Aristotle's elusiveness on the subject of how one apprehends premises of demonstrative syllogisms by commenting that the Posterior Analytics concerns scientific judgment, not scientific discovery. 49

III

Broadly speaking, Grosseteste's treatment of induction and demonstrative science represents a qualified acceptance and extension of Aristotle's doctrine in the Posterior Analytics, rather than a dramatic departure from it. Grosse-

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teste follows Aristotle in holding that demonstrative science is expressed in syllogisms which meet the various extensional and intensional requirements which Aristotle specifies. Thus the activity of the natural philosopher should consist largely in discovering the appropriate premises for demonstrative syllogisms. The most important qualifications I have noted in Grosseteste's acceptanc e of Aristotle's theory of induction and demonstrative science are his points that the theory depends critically on the assumptions that nature is uniform and that we can discriminate accurately between essential and accidental properties of substances, s 0 These are assumptions which Aristotle makes, but whose importance Grosseteste underscores. However, Grosse- teste's attachment to the Augustinian doctrine of divine illumination consti- tutes at least a variation on Aristotle's theory. But it is not immediately obvious whether this variation amounts to an extension of Aristotle's theory, an undermining of it, or a dramatic departure from it. Although I have not found enough evidence in the commentary to substantiate a definite determi- nation of this questiort, what I have found suggests that Grosseteste's illumi- nation theory amounts to an extension of the theory ot induction and demonstrative science, and does not undermine it.

One might suppose that Grosseteste's introduction of the notion of divine illumination is a religiously motivated but theoretically insignificant shift in terminology. If we follow the empiricist interpretation of nous, and note that nous characterizes the intellectual state of Aristotle's knower, while divine illumination characterizes the intellectual state of Grosseteste's knower, it is tempting to conclude that the concepts of nous and divine illumination are equivalent. But I think that there are significant differences to be discerned between nous and divine illumination. Aristotle's claims about nous in the last chapter of the Posterior Analyt ics strike me as rather modest. He says first that the potentiality by which we grasp first principles is our ability to form settled, general concepts through a process of induction based on repeated experiences, s 1 He names the state we are in when we have grasped a concept or first principle nous, explaining that nous is related to induction as episteme is related to demonstration, s 2 As I understand them, Aristotle's claims commit him only to the conditional proposition that if we have a genuine grasp of a first principle, we are in a state of nous with respect to it. But he does not commit himself to the proposition that every general impression which seems settled and self-evident constitutes having nous, the

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most certain and highest form of knowledge. One initial difference between nous and divine illumination is that divine illumination clearly admits of degree, while this does not seem tree of nous. According to Grosseteste, all intelligibles are known by some degree or other of divine illumination. 5 3 Complete knowledge is direct acquaintance with the examplars in the divine mind; ordinary human knowledge of intelligibles comprises a better or worse approximation to complete knowledge, s4 As I understand the doctrine of divine illumination, increments of illumination enhance knowledge intention- ally; that is, the knower typically accepts the same proposition as he did before the incremental illumination, but now he sees its truth more clearly, or clearly and distinctly.

I think that the difference between nous and divine illumination has several significant effects on Grosseteste's theory of demonstrative science. Paradoxically, the doctrine of divine illumination yields an account of both the corrigibility and validation of knowledge which I believe to constitute an extension of Aristotle's theory. Aristotle's account of nous does not clearly specify how one knows that one is in a state of nous; it assumes that we sometimes attain nous, since science is possible, but that we can be mistaken in our grasp of principles. While Aristotle holds that our grasp of principles is corrigible when they are mistaken, Grosseteste's theory suggests that our apprehension of principles is corrigible when they are correct. That is, his view seems to make a special place for the development of a clearer under- standing of the exact import of true principles, since it contains an explicit notion of ideal knowledge, of which our knowledge is only an approximation. Since the process of improving one's understanding involves divine illumina. tion, religious or even mystical motivations in principle can support such endeavors.

The doctrine of divine illumination can also serve as a means of validating the reliability of our demonstrative science. Grosseteste points out explicitly that demonstrative science depends on the uniformity of nature and On our ability to discriminate between essential and accidental causes, and thus use the method of division perspicuously. While Grosseteste isJfar from a full- blown Cartesian skeptic, his concern over these assumptions suggests that he has gone beyound Aristotle in raising skeptical questions about the criteria for and reliability of the principles which we consider correct and the syllogisms which we consider genuinely demonstrative. If Grosseteste believes

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that God is benevolent and does provide illumination, as I think he does, then he has a special basis for certifying the fundamental reliability of our demonstrative science, even ff it does not constitute the most direct appre- hension of exemplars.

Of course Grosseteste's validation of our efforts at demonstrative reason- ing by reference to divine illumination may not have direct practical signifi- cance for the natural philosopher, if it is as difficult to recognize when one has divine illumination as it is to tell when one has nous . It is hard to imagine that Grosseteste could deny the possibility that we are sometimes simply mistaken in supposing that a certain proposition is divinely validated. But like most divine illumination theorists, Grosseteste emphasizes the positive aspects of his view; his remarks suggest that at least some divine illumination is self- validating. That is, divine illumination carries with it a characteristic and reliably recognizable clarity and subjective certainty by which one cannot fail to recognize oneself as the recipient of divine illumination, s5 But such introspective criteria cannot stand alone in an epistemological theory; Grosse- teste must also rely on the general view that in his benevolence God provides for the reliability and corrigibility of our apprehension of principles.

Do Grosseteste's views on induction and demonstrative science have any clear significance for the rise of experimentation in science? It seems to me that the epistemology underlying Grosseteste's theory of science can have two opposing influences on the frequency of experimentation in science. Surely it is a mistake to say that Grosseteste was responsible for abandoning the search for uniquely necessitating causes of phenomena, leaving natural philosophers only the task of propounding hypotheses and disconfirming the worst of them through experiments. I see no evidence that Grosseteste does abandon Aristotle's goals, or even that he is much more conscientious than Aristotle in emphasizing the importance of seeking out falsifying counter- examples to principles. And surely Grosseteste is not motivated by skep- ticism, Humean, Popperian, or otherwise, about the justification of intuitive induction in particular. If anything, Grosseteste attributes more power and reliability to our apprehensions of principles than Aristotle does, since they can be certified by divine illumination. Of course this point relies on the assumption that divine illumination sometimes occurs, and that in general it is recognizable and reliable. But Grosseteste would have been a strange illumin. ation theorist indeed, had he not accepted these assumptions. But given these

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assumptions, Grosseteste's theory has all the utility of Aristotle's theory, with the added allure that divine aid is available to the natural philosopher, and that scientific reflection may bring him into a closer relation with God. Perhaps these additional features help explain why so many medievals dedi- cated themselves, at least in principle, to the search for uniquely necessitating causes of phenomena.

But possible unguarded assumptions about the sometimes self-validating character of divine illumination can have an opposing influence on the frequency of experimentation in science. Grosseteste's endorsement of care- ful observation is consistent with his view that certainty only arises as a result of divine illumination, since typically divine illumination only clarifies the existing contents of the mind. Hence it is indispensable for the scientist to make his observations, and to formulate principles and concepts to the best of his ability. This as a matter of course involves looking for instances which disconfirm the proposed principles. But if and when these principles and their connections acquire an ineluctable subjective clarity and force, one might mistakenly consider them to be divinely verified. Should subjective certainty arise prior to careful attempts at experimental falsification, the certain scientist might accept his principles prematurely. Thus Grosseteste's divine illumination theory might not clearly oppose the abrogation of experi- mentation in those unfortunate cases where subjective certainty arises pre- maturely and mistakenly. A" recognition of this tendency of Grosseteste's theory might mitigate the shock of learning that the one quantitative law which Grosseteste himself proposed is false, and it would have been discon- firmed by the simplest of experimental procedures, s 6

Yale University

NOTES

1 I would like to thank Marilyn Adams, Simo Knuuttila, John Longeway, John Murdoch, and Merrilee Salmon for their suggestions; and I would like to thank the Academy of Finland and the American Council of Learned Societies for their support. 2 Robert Grosseteste, In Aristotelis Posteriorum Analytieorm Libros and Walter Burleigh, Super Libros Posteriorura Analytieorum Aristotelis (Venice: 1514; reprint ed., Frankfurt/Main: Minerva G.m.b.H., 1966). For a discussion of the dating of the commentary, see B. G. Dod, The Study of Aristotle's Posterior Analyties in the twelfth

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and thirteenth centuries: the translation, glossators, and commentators, and their methods (B. Litt. Dissertation, Oxford University, 1971) p. 46 ff. 3 C.H. Lohr, 'Medieval Latin Aristotle commentaries', Traditio 28 (1972), 281-396 . 4 For full reports of the medieval latin commentaries, see C. H. Lohr, op. cit.: Traditio 23 (1967), 313-413; 24 (1968), 149-245; 26 (1970), 135-216;27 (1971), 251-351; 28 (1972), 281-396; 29 (1973), 93 -197; 30 (1974), 119-144 . s For a general survey, see D.E. Sharp, Franciscan Philosophy at Oxford in the Thirteenth Century (Oxford, 1930). 6 Crombie, pp. 132-134. 7 K. R. Popper, The Logic of Scientific Discovery (London, 1959), pp. 27 -30 . 8 For a study of issues in this text, see J. Baxnes, Aristotle's Posterior Analytics (Oxford, 1975) and K. J. J. Hintikka, 'On the Ingredients of an Aristotelian Science', Nous 6 (1972), 55 -69 . 9 For an account of what Aristotle means by 'phenomena' , see G. E. L. Owen, ' "Tithenai ta Phainomena" ' in J. Barnes et al. (eds.), Articles on Aristotle: I. Science (London, 1975), 113-126. 1 o Here I rely on J. Barnes, 'Aristotle's Theory of Demonstration', ibid. 65 -87 . ~ Posterior Analytics I, 2; I, 9.

12 ibid. I, 2; I, 6. 13 ibid. II, 12. 4 ibid. II, 8; II, 11; II, 17.

1 s ibid. I, 13. 1~ Aristotle uses more and less strict notions of 'demonstrat ion' tbxoughout the Posterior Analytics; but in its strict sense, a demonstrat ion has two premises which are principles, and its middle term is the definition of its subject.

7 An example of what a single demonstrative syllogism might look like is this: Having incisors belongs necessarily to every carnivore. Being carnivorous belongs necessarily to every dog. Therefore: having incisors belongs necessarily to every dog. See Barnes, Articles, p. 66.

8 Posterior Analytics I, 1 -3 . 1 9 ibid. II, 19. Empeiria presupposes sense perception and memory. 20 ibid. II, 13. 2 ~ ibid. II, 18 -19 . 22 Barnes, Aristotle's Posterior Analytics, pp. 256-7 . 23 ibid. 257. 24 PosteriorAnalytics I, 9. In the subsequent chapter Aristotle seems to suggest that the organization of explananda into natural kinds might somehow mitigate this difficulty. 25 Crombie, p. 71. 26 ibid. 71n. But in another note, on p. 34, Crombie seems to recognize the anachronism of attributing this Humean distinction to medieval thinkers. 27 ibid. 85. 2 s ibid. 133. 29 ibid. 134. 3o ibid. 81. 31 ibid. 85. 32 ibid. 73 -4 . 33 ibid. 82 -5 .

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34 ibid. 134. 3 s As John Longeway writes in his work Simon of Faversham's Questions on the Posterior Analytics: A Thirteenth Century View o f Science (Ph.D. Dissertation, Cornell University, 1977): "He uses the account of demonstrative science which he finds in the Posterior Analytics to analyze the Posterior Analytics, expecting the book to provide an account in demonstrative form of the science wh ichhas demonstration as its subject. This means that the essential properties of demonstrat ion are to be proven of it . . . . " p. 126. 36 Grosseteste, I, 14. 37 For example, they both assume that one will often recognize the correct explanatory definitions simultaneously with observing a phenomenon. 38 ibid. I, 12. 9 In the light of Aristotle's view, which is shared by Grosseteste, that definitions of

subjects give their formal cause, and so count as causally explanatory principles, it is hard to see how either of them could maintain this distinction. 4 o ibid. II, 2. 41 ibid. I, 7. Quoted in Crombie, pp. 130-131. 42 See Barnes, Aristotle's Posterior Analytics, pp. 221-3 . 43 Crombie, p. 81. 44 Grosseteste, II, 5. 4 s PosteriorAnalytics II, 17. 46 Grosseteste, II, 5. 47 ibid. II, 4. 48 One reason why I question whether Grosseteste takes this example seriously is that he fails to comment on the fact that Avicenna's cognitive psychology includes the notion of a distinct estimative faculty. 49 ibid. II, 6. s o Some later commentators on the Posterior Analytics quote and discuss this point. s ~ PosteriorAnalytics II, 19. 52 loc. cit. s 3 Grosseteste I, 7. s a Like most divine i l lumination theorists, Grosseteste dismisses the possibility that a genuine intellectual vision of an intelligible might be defective. An early expression of this assumption is found in Book XII, 29 and 30 of Augustine's Literal Commentary on Genesis. J. Migne, Patrologia Latina (Rome, 1906-1908) Vol. 34, Cols. 453-486 . s s Grosseteste says in I, 17 that certainty with respect to intelligibles increases in proportion to their proximity to the divine. s 6 On this subject, see B. S. Eastwood, 'Grosseteste's Quantitative Law of Refraction: A Chapter in the History of Non-experimental Science', Journal o f the History of Ideas 28 (1967), pp. 402-414 , and Richard C. Dales, 'Robert Grosseteste's Scientific Works', Isis (1961), pp. 381-402 .