For future (natural) scientists in the middle ages, the universities of Oxford and Paris were interesting places. And one of the most interesting professors of science was Roger Bacon. He used mathematics and experiments to gain new knowledge. He encouraged his students to study foreign languages and to learn from both ancient Greek philosophers and Islamic scientists, especially when it comes to optics and to experiments which shall explain the nature of light. But he is also aware that there can be prejudices and pseudo-scientific thoughts which can keep a scientist from following an objective way of thinking and studying. And this is what the following text is about. It’s the very beginning of Bacon’s “Opus Maius”, a manual for students of sciences.
1214 ADRoger Bacon was born in Ilchester, Somerset
1214 ADBouvunes’ battle
1245 ADStart living in Paris
1245 ADCouncil of Lyon
1255 ADLeaves Paris
1257 ADBacon entry into the Franciscan order, returns to Oxford and starts teaching there
1265 AD - 1268 ADThe pope released him from all prohibitions and limitations imposed upon him by his superiors in the Franciscan order. He asked him to send his work, of which he heard, to Viterbo.
1265 AD - 1268 ADPontificate of Pope Clement IV Montaperti’s battle Benevento’s battle (Angioinis won the battle)
1266 AD-1268 ADHe wrote Opus maius, Opus minus, and Opus tertium.
1268 ADHe started to write Communia Naturalium, Communia Mathematica
1271 ADHe wrote Compendium studii philosophiae
1277 ADJerome of Ascoli, the General of the Franciscans, again condemned Bacon’s doctrine
1289 ADBacon was confined until this date
1289 ADCampaldino’s battle (Guelfi’s troops defeated Ghibellini’s troops)
1292 ADBacon died in Oxford, where was buried
OPUS MAIUS I 1
 Ex his autem pestibus mortiferis accident omnia mala humano generi: nam ignorantur utilissima et maxima et pulcherrima sapientiae documenta et omnium scientiarum et artium secreta.
 Sed peius est, quod homines horum quatuor caligine excaecati non percipiunt suam ignorantiam, sed cum omni cautela palliant et defendunt, quatenus remedium non inveniant.
 Et quod pessimum est: cum sint in tenebris errorum densissimis , aestimant se esse in plena luce veritatis.
 Propter quod verissima reputant esse in fine falsitatis, optima nullius valoris, maxima nec pondus nec pretium obtinere et e contario falsissima celebrant, pessima laudant, extollunt, vilissima caecutientes aliud esse omnem sapientiae fulgorem, fastidientes quae magna facilitate possunt adipisci.
 Et propter stultitiae magnitudinem ponunt summos labores, consumunt tempora multa, magnas expensas effundunt in iis, quae nullius utilitatis vel parvae sunt nec dignitatis alicuius secundum iudicium sapientis.
 Et ideo necesse est, ut violentia et malitia harum quatuor causarum omnis mali cognoscantur in principio et reprobentur et longe a consideratione sapientiae relegentur.
 Nam ubi haec tria dominantur, nulla ratio movet, nullum ius indicat, nulla lex ligat, fas locum non habet, naturae dictamen perit, facies rerum mutatur, ordo confunditur, praevalet vitium, virtus extinguitur, falsitas regnat, veritas exsufflatur.
 Et ideo nihil magis necessarium est considerationi, quam certa damnatio istorum quatuor per sententias sapientium electas, quibus non poterit contradici.
 To tell the truth, from these deadly epidemics happen all the bad things to human beings: in fact the most useful, the biggest and the most beautiful documents of wisdom are ignored and those of all the sciences and arts are secret.
 But it is worse that men, made blind by the fog of these four vices, do not perceive their ignorance, but they hide it and defend it with every type of device until they find a solution.
 And the worst is that even if men are sur rounded by the most dense shadow of mistake, they believe to be in the full light of truth.
 Therefore, they consider the absolutely true things being false, the best one being without value, the biggest one having no importance nor price and, on the contrary, they praise the most false, they worship the worst ones, they raise the most coward, as they do not see that all the light of knowledge is another, as they are annoyed by those which they can understand easily.
 And, due to the hugeness of their stupidity, they undertake the biggest labours, waste a lot of time, pour off a lot of money in those things, which have not got any utility or are insignificant nor have any dignity according to the wise men.
 Thus, it is necessary to know from the beginning the violence and the malice of these four motivations of every bad thing and to condemn and to relegate them far from the consideration of knowledge.
 Indeed, where these things are established, no reason can move, no right can judge, no law can impose, there is no right, the natural order dies, the appearance of reality changes, the order gets confused, the vice prevails, the virtue switches off, the falsehood rules, the truth blows away.
 Thus, nothing is more necessary for our analysis than an absolute condemnation of these four causes according to the considerations of the wise men, which can not be contradicted.
Perotin, Viderunt omnes, 13th century
Roger Bacon moved to Paris in 1245. At that time the Polifonic School of Notre Dame of Paris was one of the most important centres of music culture of all Europe. Students from all over the continent came there to study all the innovations about polyphony and notation. Perotin was a magister of the school and he contributed to increase the Magnus Liber Organi, a collection of ancient polyphonic compositions made by his predecessor Leonin.