Robert Grosseteste

Robert Grosseteste (c. 1175 – 1253) was an English statesman, scholastic philosopher, theologian, scientist, pastor, poet, educator and Bishop of Lincoln, Province of Canterbury, England. From about 1220 to 1235 he wrote a host of scientific treatises and was an early supporter of what was to become the scientific method. Roger Bacon expressed his indebtedness to the work of Grosseteste and A.C. Crombie describes him as "the real founder of the tradition of scientific thought in medieval Oxford..."

Translations of Robert Grosseteste's quotes in this article are due to A.C. Crombie, Robert Grosseteste and the Origins of Experimental Science 1100-1700 (1953) unless otherwise noted.

• Just as the light of the sun irradiates the organ of vision and things visible, enabling the former to see and the latter to be seen, so too the irradiation of a spiritual light brings the mind into relation with that which is intelligible.
  • Commentary on Aristotle's Posterior Analytics, i.17 as quoted by Francis Seymour Stevenson, Robert Grosseteste: Bishop of Lincoln, p. 52 (footnote 2)

• The consideration of lines, angles and figures is of the greatest utility since it is impossible for natural philosophy to be known without them... All causes of natural effects have to be given through lines, angles and figures, for otherwise it is impossible for the reason why (propter quid) to be known in them.
  • De Lineas, Anguilis et Figuris (On Lines, Angles and Figures) as quoted in Neil Lewis, "Robert Grosseteste" Stanford Encyclopedia of Philosophy (2007, 2013) citing Baur, Ludwig (ed.) Die Philosophischen Werke des Robert Grosseteste, Bischofs von Lincoln (1912) pp.59–60

• Power from natural agents may go by a short line, and then in its activity greater... But if by a straight line then its action is stronger and better, as Aristotle says in Book V of the Physics, because nature operates in the shortest way possible. But the straight line is the shortest of all, as he says in the same place.
  • De Lineas, Anguilis et Figurisas quoted by A.C. Crombie, Robert Groseesteste and the Origins of Experimental Science 1100-1700 (1953) citing Baur, Ludwig (ed.) Die Philosophischen Werke des Robert Grosseteste, Bischofs von Lincoln (1912)

• This part of optics, when well understood, shows us how we may make things a very long distance off appear as if placed very close, and large near things appear very small, and how we may make small things placed at a distance appear any size we want, so that it may be possible for us to read the smallest letters at incredible distances, or to count sand, or seed, or any sort of minute objects.
  • De iride (On the rainbow) Note this prediction of optical scientific instruments like the telescope and microscope, not to be utilized until 250 years later.

• Every operation in nature is in the shortest, best ordered, briefest, and best possible way.
  • De iride published in Beiträge zur Geschichte der Philosophie des Mittelalters, IX (1912) pp.74-75 as quoted in Carl B. Boyer, The Rainbow: From Myth to Mathematics (1959)

• The diligent investigator of natural phenomena can give the causes of all natural effects... by the rules and roots and foundations given from the power of geometry.
  • On the Nature of Places, a continuation of the treatise On Lines, Angles and Figures as quoted by Amelia Carolina Sparavigna, "Translation and discussion of the De Iride, a treatise on optics by Robert Grosseteste" arXiv:1211.5961v1 @arXiv.org, Cornell University (2012)

• The head is borne towards the heavens and has two lights, as it were the sun and moon.
  • As quoted by J. J. McEvoy, The philosophy of Robert Grosseteste (1982) p. 372.

(Light or the Beginnings of the Forms)

• The first corporeal form, which some call corporeity, I hold to be light. For light of its own nature diffuses itself in all directions, so that from a point of light a sphere of light of any size may be instantly generated, provided an opaque body does not get in the way. Corporeity is what necessarily follows the extension of matter in three dimensions, since each of these, that is corporeity and matter, is a substance simple in itself and lacking all dimensions. But simple form in itself and in dimension lacking matter and dimension, it was impossible for it to become extended in every direction except by multiplying itself and suddenly diffusing itself in every direction and in its diffusion extending matter; since it is not possible for form to do without matter because it is not separable, nor can matter itself be purged of form. And, in fact, it is light, I suggest, of which this operation is part of the nature, namely, to multiply itself and instantaneously diffuse itself in every direction. Therefore, whatever it is that produces this operation is either light itself or something that produces this operation in so far as it participates in light, which produces it by its own nature. Corporeity is therefore either this light, or is what produces the operation in question and produces dimensions in matter in so far as it participates in this light itself and acts by virtue of this same light. But for the first form to produce dimensions in matter by virtue of a subsequent form is impossible. Therefore light is not the form succeeding this corporeity, but is this corporeity itself.

• One cause, in so far as it is one, is productive of only one effect. I do not rule out several efficient causes of which one is nearer and another more remote in the same order. Thus when I say simply 'animal', I do not exclude another substance or particular substance. Hence motion, in so far as it is one, is productive of only one effect. But motion is present in every body from an intrinsic principle which is called natural. Therefore an efficient cause simply proportional to the motion is present in all bodies. But nothing is present in common in every body except primitive matter and primitive form and magnitude, which necessarily follows from these two, and whatever is entailed by magnitude as such, as position and shape. But simply through magnitude a body does not receive motion, as is clear enough when Aristotle shows that everything that moves is divisible, not, therefore, simply because of magnitude or something entailed by magnitude is a body productive of motion. Nor is primitive matter productive of motion, because it is itself passive. It is therefore necessary that motion follow simply from the primitive form as from an efficient cause.

• I hold that the first form of a body is the first corporeal mover. But this is light, which as it multiplies itself and expands without the body of matter moving with it, makes its passage instantaneously through the transparent medium and is not motion but a state of change. But, indeed, when light is expanding itself in different directions it is incorporated with matter, if the body of matter extends with it, and it makes a rarefaction or augmentation of matter; for when light is itself charged with the body of matter, it produces condensation or rarefaction. So when light generates itself in one direction drawing matter with it, it produces local motion; and when light within matter is sent out and what is outside is sent in, it produces qualitative change. From this it is clear that corporeal motion is a multiplicative power of light, and this is a corporeal and natural appetite.
  • see De Luce Tr. Ludwig Baur (1912) pp. 51-52

(Commentary on [Aristotle's] the Posterior Analytics Books)

• I say that it is possible to have some knowledge without the help of the senses. For in the Divine Mind all knowledge exists from eternity, and not only is there in it certain knowledge of universals but also of all singulars. ...Similarly, intelligence receiving irradiation from the primary light see all knowable things, both universal and singulars, in the primary light itself. Moreover, the Divine Mind, in the reflection of its intelligence upon Itself, knows the very things which come after Itself, because it is itself their cause. Therefore, those who are without any senses have true knowledge.

• The highest part of the human soul, which is called the intelligence and which is not the act of any body and does not need for its proper operation a corporeal instrument—this intelligence, if it were not obscured and weighed down by the mass of the body, would itself have complete knowledge from the irradiation received from the superior light without the help of sense, just as it will have when the soul is drawn forth from the body, and as perhaps those people have who are free from the love and the imaginings of corporeal things.

• Because the purity of the eye of the soul is obscured and weighed down by the corrupt body, all the powers of this rational soul born in man are laid hold of by the mass of the body and cannot act and so in a way are asleep. Accordingly, when in the process of time the senses act through many interactions of sense with sensible things, the reasoning is awakened mixed with these very sensible things and is borne along in the senses to the sensible things as in a ship. But the functioning reason begins to divide and separately consider what in sense were confused. ...But the reasoning does not know this to be actually universal except after it has made this abstraction from many singulars, and has reached one and the same universal by its judgement taken from many singulars.

• The experimental universal is acquired by us, whose mind's eye is not purely spiritual, only through the help of the senses. For when the senses several times observe two singular occurrences, of which one is the cause of the other or is related to it in some other way, and they do not see the connection between them... And from this perception repeated again and again and stored in memory, and from the sensory knowledge from which the perception is built up, the functioning of the reasoning begins. The functioning reason therefore begins to wonder and to consider whether things really are as the sensible recollection says, and these two lead the reason to experiment... But when he has administered many times with the sure exclusion of all other things [that could be mistaken for the cause]... then there is formed in the reason this universal... and this is the way in which it comes from sensation to a universal experimental principle.
  • i. 14, ff. 13^vb-14^rb.

• That is better and more valuable which requires fewer, other circumstances being equal, just as that demonstration is better, other circumstances being equal, which necessitates the answering of a smaller number of questions for a perfect demonstration or requires a smaller number of suppositions and premises from which the demonstration proceeds. For if one thing were demonstrated from many and another thing from fewer equally known premisses, clearly that is better which is from fewer because it makes us know quickly, just as a universal demonstration is better than particular because it produces knowledge from fewer premises. Similarly in natural science, in moral science, and in metaphysics the best is that which needs no premisses and the better that which needs the fewer, other circumstances being equal.
  • i. 17, f. 17^vb

• Ostensive demonstration is that which concludes directly to that which is in question. Reduction ad impossibile is that which, when something the opposite of that which is in question has been assumed, concludes with some other proposition directly to a known and manifest impossibility, from the opposite of which the investigator is led back to the original proposition in question. But there is a difference between ostensive demonstration and reduction ad impossibile, because the former proves from things prior in the order of nature but the latter from things posterior in the order of nature. When things prior in nature are better known in the intellect of the person making the demonstration the process is carried out ostensively; but when posterior things are better known to his intellect then the demonstration is carried out per impossibile... in demonstration carried out per impossibile the showing of the original thing in question is carried out by means of things posterior to it in the order of nature... And there is in the contrary, falsely supposed in predicate of subject, a connecting term by which something is implied to be which impossible in the nature of things.
  • i. 17, f. 18^r

(The liberal arts)

• And since the proportions of the human voice and the gesticulations of the human body are regulated by the same modulation as that by which sound and the motion of other bodies are, musical thought is subalternated not only to the harmony of human voice and gesticulation, but also of instruments and of those whose delectation consist in motion or sound and with these the harmony of the celestial and non-celestial. And since the concordance of times and the composition and harmony of the lower world and of all things composed of four elements come from celestial motions, and, moreover, since it is necessary to find the harmony of causes in their effects, the study of music also extends to knowing the proportions of times and the constitution of the elements of the lower world, and even the composition of all the elements.
  • As quoted by Tanner, Bower, McLeish, and Gaspar in Ch. 1. "Unity and Symmetry in the De Luce of Robert Grosseteste," Robert Grosseteste and the pursuit of Religious and Scientific Learning in the Middle Ages (2016) ed., Jack P. Cunningham, Mark Hocknull, p. 17.

(Commentary on Aristotle's 8 Books of Physics)

• Vacuum stands and remains a mathematical space. A cube placed in a vacuum would not displace anything, as it would displace air or water in a space already containing those fluids.

• In a vacuum which is imagined as infinite there cannot be local differences, both on account of its infinity, and also because of the fact that the vacuum, if it exists, would have no nature but a privation, and therefore it can have no natural differences.

• The space of the real physical world must be considered full, that is a plenum, because a vacuum could have no physical existence.

• The Greek and Hebrew he did not know sufficiently to translate them unassisted, but he had many assistants.
  • Roger Bacon, Compendium Studii Theologiae (1292) (Compendium of the Study of Theology) c. viii. as cited by George Gresley Perry, The Life and Times of Robert Grosseteste, Bishop of Lincoln (1871)

• One man alone had really known the sciences, namely, Robert, Bishop of Lincoln.
  • Roger Bacon, Opus Tertium (c. 1267) p. 33 Cp. Opis Majus (c. 1267) ed. Jebb p. 45; ed. Bridges, i. p. 67

• Few have attained to consummate wisdom in the perfection of philosophy: Solomon attained to it, and Aristotle in relation to his times, and in a later age Avicenna, and in our own days the recently deceased Robert, Bishop of Lincoln, and Adam Marsh.
  • Roger Bacon, Opus Tertium (c. 1267) p. 70

• No one really knew the sciences except the Lord Robert, Bishop of Lincoln, by reason of his length of life and experience, as well as of his studiousness and zeal. He knew mathematics and perspective, and there was nothing which he was unable to know; and at the same time he was sufficiently acquainted with languages to be able to understand the saints and the philosophers and the wise men of antiquity but his knowledge of languages was not such as to enable him to effect translations until the latter portion of his life...
  • Roger Bacon, Opus Tertium (c. 1267) p. 91

• There were found some famous men, such as Robert, Bishop of Lincoln, and Adam Marsh, and several others, who were aware that the power of mathematics is capable of unfolding the causes of all things, and of giving a sufficient explanation of human and divine phenomena; and the assurance of this fact is to be found in the writings of those great men, as, for instance, in their works on the impressions on the rainbow and the comets, on the generation of heat, on the investigation of geography, on the sphere, and on other questions appertaining both to theology and to natural philosophy.
  • Roger Bacon, Opus Majus (c. 1267) ed. Jebb, p. 64; ed. Bridges, i. p. 108.

• Robert Grosseteste... was born at the decisive moment when Greek and Arabic science became accessible in Latin versions.
  • Carl B. Boyer, The Rainbow: From Myth to Mathematics (1959)

• Robert became much interested in science and scientific method; and he showed particular attention to optics, which he regarded as the key to an understanding of the physical world. He was conscious of the dual approach by means of induction and deduction (resolution and composition); i.e., from the empirical knowledge one proceeds to probable general principles, and from these as premises one them derives conclusions which constitute verifications or falsifications of the principles. This approach to science was not that far removed from Aristotle...
  • Carl B. Boyer, The Rainbow: From Myth to Mathematics (1959)

• I shall tell, as I have herd
  Of the byshop Saint Roberd;
  His tonaine is Grossteste,
  Of Lyncolne so seyth the geste:
  He loved moche to here the harpe,
  For mannes wit it makyth sharpe;
  Next hys chamber, besyde hys study
  Hys harper's chamber was fast the by.
  Many tymes, by nightes and dayes,
  He hadd solace of notes and layes.
  On asked hyme the reason why
  He had delyte in mynstrelsy;
  He answered hym in this manere
  Why he held the harpe so dere:
  The virtu of the harpe, through skyll and ryght,
  Will destrye the fendy's myght;
  And to the cros, by gode skeyl,
  Ys the harpe lykened well.
  • Robert de Brune (Robert Manning of Bourne), "Handlyng Synne" (1303)

• Grosseteste's contribution was to emphasize the importance of falsification in the search for true causes and to develop the method of verification and falsification into a systematic method of experimental procedure.
  • A.C. Crombie, Robert Grosseteste and the Origins of Experimental Science 1100-1700 (1953)

• The strategic act by which Grosseteste and his thirteenth- and fourteenth-century successors created modern experimental science was to unite the experimental habit of the practical arts with the rationalism of twelfth-century philosophy.
  • A.C. Crombie, Robert Grosseteste and the Origins of Experimental Science 1100-1700 (1953)

• Groesseteste appears to have been the first medieval writer to recognize and deal with the two fundamental methodological problems of induction and experimental verification and falsification which arose when the Greek conception of geometrical demonstration was applied to the world of experience. He appears to have been the first to set out a systematic and coherent theory of experimental investigation and rational explanation by which the Greek geometrical method was turned into modern experimental science. As far as is known, he and his successors were the first to use and exemplify such a theory in the details of original research into concrete problems.
  • A.C. Crombie, Robert Grosseteste and the Origins of Experimental Science 1100-1700 (1953)

• In its application to natural science Grosseteste based his method of verification and falsification on two assumptions about the nature of reality. (a) The first was the principle of the uniformity of nature, meaning that forms are always uniform in their operations. ...In support of this principle he quoted 'Aristotles II de Generat.: ...'the same cause, provided it remains in the same condition, cannot produce anything but the same effect.' (b) The second assumption Grosseteste made was that of the principle of economy, or lex parsimoniae. This he also derived from Aristotle, who stated it as a pragmatic principle.
  • A.C. Crombie, Robert Grosseteste and the Origins of Experimental Science 1100-1700 (1953)

• By this lux as the first corporeal form Grosseteste did not, of course, mean simply visible light. As an emanation or propagation of substance and power lux was the basis of all bodily magnitude and of all natural operations, of which the manifestation of visible light was only one. One of the most important functions of lux was to be the intermediary between spirit and matter. It was the instrument by which God produced the macrocosm of the universe, and the instrument by which the soul made contact with the physical body and the things of sense in the microcosm of man.
  • A.C. Crombie, Robert Grosseteste and the Origins of Experimental Science 1100-1700 (1953)

• [Grosseteste] far surpassed all the philosophers of his time, and outstripped all theologians in divine knowledge and doctrine. His most famous works remain to testify this to scholars of our day, and by virtue of his genius, which was wonderfully strengthened by divine grace, he might say 'I have more understanding than all my teachers.' But most of all did he excel in humility, simplicity, and sanctity, so that he passed his life in innocency, chastity, and purity.
  • Dean and Chapter of St Paul's letter to Clement V in support of Grosseteste's canonization (1307) as quoted in Robert Grosseteste: Bishop of Lincoln by Francis Seymour Stevenson (1899)

• [Grosseteste is] excelling in merits, illustrious for holiness of life, like the morning star discerned through a gap in the clouds, like a candle not put under a bushel, but on a candlestick, that all may see the light.
  • Edward I's letter in support of Grosseteste's canonization (1307) as quoted in Robert Grosseteste: Bishop of Lincoln by Francis Seymour Stevenson (1899)

• In the thirteenth century Robert Grosseteste wrote a book on the rainbow that began an outburst of European speculation parallel to the equally rich Arab work.
  • Philip Fisher, Wonder, the Rainbow, and the Aesthetics of Rare Experiences (1998)

• Robert Grosseteste affirmed and refined Aristotle's inductive-deductive method, which he termed the Method of Resolution and Composition for its inductive and deductive components, respectively. But he added to Aristotle's methods of induction. His purposes were to verify true theories and to falsify false theories. Causal laws were suspected when certain phenomena were frequently correlated, but natural science sought robust knowledge of real causes, not accidental correlations. ...His approach used deduction to falsify proposed but defective inductions. ...Grosseteste's Method of Verification deduced consequences of a theory beyond its original application and then checked those predictions experimentally. His Method of Falsification eliminated bad theories by deducing implications known to be false. Grosseteste clearly understood that his optimistic view of induction required two metaphysical presuppositions about the nature of physical reality: the uniformity of nature and the principle of parsimony or simplicity. Without those presuppositions, there is no defensible method of induction in particular or method of science in general.
  • Hugh G. Gauch, Scientific Method in Brief (2012)

• Although Grosseteste's science could be decidedly Aristotelian, he also was clearly an independent thinker. For example, Grosseteste viewed light as metaphysical phenomenon, holding that God created light as the universe's first, incipient material form, and that light subsequently diffused from a single point to create the natural world. There were several precedents for this Neoplatonic belief in light as the primeval manifestation of God, among them the writings of Saint Augustine. Thus for Grosseteste the study of light and optics was a means of understanding God's handiwork.
  • Raymond L. Lee & Alistair B. Fraser, The Rainbow Bridge: Rainbows in Art, Myth, and Science (2001)

• Grosseteste was the first medieval writer to break with the ancient tradition of discounting refraction in the rainbow. In another way, however, Grosseteste is firmly bound to his predecessors' rainbows—an experimentalist in principle, in practice he strays very little from the Aristotelian tradition of selective observation constrained by geometry. Furthermore, Grosseteste's rainbow theory often appeals to authority, leading historian Bruce Eastwood to remark: "When sources fail, he invents, and the invention is never contradictory to literary sources." (In fairness, Grosseteste made several observations about the rainbow that gainsaid ancient authority.)
  • Raymond L. Lee & Alistair B. Fraser, The Rainbow Bridge: Rainbows in Art, Myth, and Science (2001)

• Grosseteste was deeply concerned with the detailed investigation of natural phenomena. It was the inspiration of this attitude of mind, together with Grosseteste's emphasis on the importance of mathematics, that was perhaps his chief legacy to thinkers in fourteenth-century Oxford who were developing the beginnings of a mathematical physics.
  • Neil Lewis, "Robert Grosseteste" Stanford Encyclopedia of Philosophy (2007, 2013)

• There is scarcely a character in English history whose fame has been more constant, both during and after his life, than Robert Grosseteste, Bishop of Lincoln from 1235 to 1253. As we find his advice sought universally during his lifetime, and his example spoken of as that which almost all the other prelates of his day followed, so was it also after his death. If threats from Rome and excommunications from Canterbury fell harmlessly upon him while alive, his example nerved others in subsequent years—as in the case of Sewal, Archbishop of York—to bear even worse attacks without giving way. And probably no one has had a greater influence upon English thought and English literature for the two centuries which followed his time; few books will be found that do not contain some quotations from Lincolniensis, 'the great clerk, Grostest.'
  • Dr. Luard, Preface to Grosseteste's Letters. Rolls' Series (1861) as quoted in Robert Grosseteste: Bishop of Lincoln by Francis Seymour Stevenson (1899)

• Grosseteste aimed consciously at producing a synthesis of the cosmogony of Genesis and the cosmology of [ Aristotle's ] De Caelo. ...His intution led him to the conviction that mathematics, far from being an abstraction from aspects of the physically real, is the very internal texture of the natural world, presiding over its coming to be and controlling its functioning, that, in the words of Kepler, 'Ubi materia, ibi geometria' [Where there is matter, there is geometry]. Of course, this faith was metaphysical; but then so to was much of the high-level inspiration of scientists in the seventeenth century. It was abstract, because the mathematical structure of reality is not given to the senses, but intuited in or believed by the mind. What it afforded was not so much scientific results as delight in the pure understanding of the essence of things, and, what Grosseteste valued most of all, a glimpse beyond the beauty of the harmonious textura of things to the mind of the primus numerator [premier calculator], the lux prima et inaccessibilus [first and inaccessible light]. The novel aspect of Grosseteste's world-system goes back entirely to this conception of God as the great calculator. For the first time, it would appear, in the history of Christian belief, God is addressed as a mathematician whose ideas for creation are mathematical operations realizable in matter and form.
  • James J. McEvoy, The Philosophy of Robert Grosseteste (1982) p. 152, 154

• He was an open confuter of both Pope and King, the corrector of monks, the director of priests, the instructor of clerks, the supporter of scholars, a preacher to the people, a persecutor of the incontinent, the unwearied student of the Scriptures, a hammer and despiser of the Romans. At the table of bodily refreshment he was hospitable, eloquent, courteous, pleasant, and affable; at the spiritual table devout, tearful, and contrite. In the episcopal office he was sedulous, dignified, and indefatigable.
  • Matthew Paris, Hist. Maj. v.407; see also Chronica Majora

• He lived in a corrupt age, and he aspired to be the great reformer of the Church of his day as his friend Simon de Montfort was of the State. ...Robert Grosseteste was also the most learned man of his time, not only in England, but in all Europe, and one of the most voluminous writers that England has produced. He was the greatest theologian, the greatest natural philosopher, the greatest master of language, of his day. His works which are almost all still imprinted are more than 200 in number and are upon almost every subject of theology and science.
  • George Gresley Perry, The Life and Times of Robert Grosseteste, Bishop of Lincoln (1871)

• The name which he afterwards acquired being doubtless due to the peculiarity of his personal appearance, the largeness of his head. Matthew Paris speaks of him as "Robert who is known by the surname of Grosseteste," or "Robert called Great-Head." Nicholas Trivet says, "he was surnamed by many Great-Head."
  • George Gresley Perry, ibid.

• Robert Grossetest... described a compelling, unified version of the universe in which light was the fundamental force. Differing from Aristotle and others who had argued that heavenly bodies consisted of some pure, quintessential substance unlike any found on Earth, Grosseteste maintained that the stars themselves are composed of the four earthly elements. Like the attraction of a lump of iron to a magnet, light from the stars attracts comets, which themselves are a form of purified fire. His model also explained the moon's influence on the tides in terms of the way its light causes water to swell and move upward.
  • Ivars Peterson, Newton's Clock: Chaos In The Solar System (1993)

• Robert Grosseteste. Robert Grosthead or Greathead. Robert Grosse capitas Lincolniensis. ...first chancellor of the University of Oxford; first lecturer to the Oxford Franciscans. ...English mathamatician, astronomer, physicist, philosopher, translator from Greek into Latin. He was the main organizer of philosophical studies at Oxford, and his influence was strongly felt in England for at least a couple of centuries. Nor was it limited to England. His insistence on the necessity of studying Greek and basing natural philosophy upon mathematics and experiment was extremely beneficial and far-reaching; in this he was clearly the forerunner of his most famous pupil, Roger Bacon. We may say that he influenced the whole western world, partly through his own writings, and partly through these new tendencies emphasized by Bacon and others.
  • George Sarton, Introduction to the History of Science (1927) Vol.2, pt.2, p. 583

• A large number of writings are ascribed to him; allowing for the fact that some are probably apocryphal, his literary activity must have been tremendous. He wrote commentaries on the Posterior Analytics, and on the Physics of Aristotle. His treatise on the compotus (c. 1232) includes a discussion of the reform of the calendar, which was repeatedly quoted by subsequent writers from Bacon to Peter of Ailly. … The majority of his scientific treatises deal with physical and meteorological questions. ...He was much concerned with the complex subject called "perspective" and with optical questions in general. He was well aware of the magnifying properties of lenses, a knowledge which he probably transmitted to Bacon. (Which suggests that other items of Bacon's encyclopedic knowledge were probably obtained from Grosseteste). Many of these physical writings were ascribed by Bacon collectively to Grosseteste and to Adam Marsh. Grosseteste... showed interest in astrology and alchemy, but was remarkably free from magical fancies.
  • George Sarton, Introduction to the History of Science (1927) Vol.2, pt.2, pp.583-584

• His main reason for advocating the study of Hebrew was to promote the conversion of the Jews. He was not hostile to the latter, and saved many of them from being massacred. ...Robert was not simply a great scholar, but a courageous man. He did not fear to repress the evil tendencies of his flock, nor reprove those of the Roman curia.
  • George Sarton, Introduction to the History of Science (1927) Vol.2, pt.2, p. 584

• Lux was probably Grosseteste's ingenious substitute for the immaterial pneuma of the Neoplatonists and the 'animal spirits' of medical writers.
  • Dorothea Elizabeth Sharp, Franciscan Philosophy at Oxford in the Thirteenth Century (1930)

• Grosseteste's experimental method was quite different from a method of controlled experiment. Grosseteste made no use of such a method in his writings, deriving his conclusions on the basis of a mix of considerations, appealing to authority and everyday observation (the Latin “experimentum”). He made use of thought experiments and certain metaphysical assumptions, such as the assumption of a principle of “least action.”
  • Amelia Carolina Sparavigna, "Translation and discussion of the De Iride, a treatise on optics by Robert Grosseteste" citing Neil Lewis, "Robert Grosseteste" Stanford Encyclopedia of Philosophy (2007, 2013)

• In 1307 a general application was made to Clement V. for the purpose by the Dean and Chapter of Lincoln, who sent one of their number, Robert de Killingworth, to Rome with that object and also by the Dean and Chapter of St Paul's, London, the Abbot and convent of Osney, King Edward the First, Greenfield, Archbishop of York, and the University of Oxford. ...The most interesting testimony is that from the University of Oxford, which says that he never did anything connected with the office he held or his pastoral care through fear of any man, and that he was ready, if need be, to suffer martyrdom for what he believed to be right. It also speaks of his magnificent services to the cause of science, and of the admirable character of his "regency" at Oxford. What was the precise influence which prevented his canonisation is unknown, though his attitude of sturdy independence may have contributed to the result.
  • Francis Seymour Stevenson, Robert Grosseteste: Bishop of Lincoln (1899)

• The treatise on light (De luce)... reflects a significant influence of Aristotle's scientific thinking. ...Its model of the expanding universe stimulated speculation as to whether Georges Lemaître in 1927... was aware of Grosseteste's thinking when he introduced the modern 'Big Bang' model... Grosseteste develops the consequences of his metaphysics of light towards a physics of light... This connection between the perfect heavens and the imperfect earth is an astonishing intellectual feat, rooted on the premise that there exists a fundamental unity...
  • Tanner, Bower, McLeish, and Gaspar, Introduction to Ch. 1. "Unity and Symmetry in the De Luce of Robert Grosseteste," Robert Grosseteste and the pursuit of Religious and Scientific Learning in the Middle Ages (2016) ed., Jack P. Cunningham, Mark Hocknull, p. 3.

• He was a man of excellent wisdom, and of most lucid power of teaching, as well as a pattern of all virtue. The good abilities which he had from nature he cultivated by the precepts of Scripture, so as to form a noble soul. When he was Master of Arts he wrote briefly upon the 'Book of Posterior Analytics.' He also put forth treatises on the 'Sphere,' the 'Art of Reckoning,' and many other things useful in philosophy. He was a doctor skilled in three tongues, the Latin, the Hebrew, and the Greek; and many things did he bring forth from the tongue of the Hebrews and caused many to be translated from the Greek.
  • Nicholas Trivet, Chronicle from Dacherii Spirilegio vii. 397. as cited by George Gresley Perry, The Life and Times of Robert Grosseteste, Bishop of Lincoln (1871)

• To compare him to the modern doctors is as the comparison of the sun to the moon when it is eclipsed.
  • John Tyssyngton, as quoted in The Life and Times of Robert Grosseteste, Bishop of Lincoln by George Gresley Perry, citing Wood, Annals i. 202.

• Light, according to Grosseteste, was the first form of corporeity, and from it all else followed. Multiplying itself from a single point infinitely and equally on all sides, light formed a sphere and together with this action arose matter. Following the expansion of light to its ultimate extent came a phase differentiation caused by condensation and rarefaction, which led in turn to the separation of the heavens and earth...
  • Arthur Zajonc, Catching the Light: The Entwined History of Light and Mind (1993)

• Robert Grosseteste... stands, Janus-headed, facing two directions. One face... evoking a metaphysics of light that embraces hosts of angelic beings and emanations of light that are active in God's creation... His other face gazes earthward to a future... a mathematical physics grounded in experimental observation.
  • Arthur Zajonc, Catching the Light: The Entwined History of Light and Mind (1993)

• A. C. Crombie (Alistair Cameron), 1915-1996 Robert Grosseteste and the origins of experimental science, 1100-1700 (1953)
• The Electronic Grosseteste: Texts
• Neil Lewis, "Robert Grosseteste" (2007, 2013) Stanford Encyclopedia of Philosophy
• George Gresley Perry, The Life and Times of Robert Grosseteste, Bishop of Lincoln (1871)
• Dorothea Elizabeth Sharp, Franciscan Philosophy at Oxford in the Thirteenth Century (1930)
• Amelia Carolina Sparavigna, "Translation and discussion of the De Iride, a treatise on optics by Robert Grosseteste" arXiv:1211.5961v1 @arXiv.org, Cornell University (2012)
• Francis Seymour Stevenson, Robert Grosseteste: Bishop of Lincoln (1899)