The controversy did not stop here but went much further, in both time and content. Galileo, in his Discourse on Comets had not spared his adversary, Grassi, and even less the real target of his arrows, Tycho Brahe, dead and buried for him both in reality and metaphorically. Not even the Jesuit Collegio Romano was safe from attack, owing to a number of errors committed in the school of mathematics concerning the telescopic observation of comets. Hostility and resentment against Galileo obviously mounted in Jesuit circles and in this poisonous atmosphere the idea was formed of making a reply, which was entrusted once again to Father Grassi, who later in 1619 published the Libra astronomica ac philosophica [The Astronomical and Philosophical Weighing Scales] under the pseudonym of Lothario Sarsi. While the title seemed to imply calm, thoughtful consideration (an attitude claimed by the author at every step) in weighing the various theories on comets, in reality the work breathed rancour from every comma. Although justly noting certain logical inconsistencies found in the Discourse, which was indeed casual with regard to the development of the argument, the Libra was still based on the usual scholastic canons, and thus had few means apart from verbal aggression of combating the deep-seated objections cited by Galileo and Guiducci.

 

Galileo was to reply in turn, not immediately, but a few years later in 1623, under the patronage of the Academy of the Lincei, which dedicated the work to the new Pope Urban VIII, the former Maffeo Barberini, the cardinal who, on the occasion of the unfortunate events of 1616, had been one of the less radical opponents of the Copernican theories. According to a letter from the academician Francesco Stelluti, Father Grassi, on seeing merely the frontispiece of the newly published volume, 'changed colour', because, if the content matched the title, for him there was little to celebrate. Galileo had written The Assayer, in which are weighed with a fine and accurate balance the contents of ' The Astronomical and Philosophical Weighing Scales (libra)' of Lothario Sarsi of Siguenza. The assayer was the goldsmith's precision balance, the libra was the greengrocer's scales. With this preliminary word play, Galileo revealed his intentions, which were to combat the coarse arguments of his rival with scientific rigour. The cutting, ironic tone of the text is deceptive: it was not a blow by blow response to Grassi's animosity. Galileo enjoyed suggesting to him other titles for his work, such as The Ast ronomical and Philosophical Scorpion, referring to the poisonous bites he had been given, playing on the double meaning in the names of the constellations (Libra was also the Latin name for the zodiacal sign of the Scales), but, notwithstanding this impertinent and occasionally heavy manner, he replied point for point to the whole treatise. Going far beyond the question of comets from which it started, The Assayer is a true discourse on method. It launched a frontal attack on the Aristotelian mode of proceeding in naturalist investigations adopted by Catholic culture, now made obsolete by events and kept artificially alive, for reasons that had nothing to do with any desire to find the true causes of phenomena. Fitting material for scientific research was not, for Galileo, the work of poets, 'such as the Iliad and Orlando Furioso, books in which the least important thing is whether what is written in them is true or not', but 'this greatest book that lies constantly open before our eyes', that is, the universe. In the past, Galileo had already commented ironically on the library naturalists, who never wished to 'lift their eyes from those papers, almost as if this great book of the world had been written by nature only to be read by Aristotle.'

 

Galileo's knife was double-edged. It struck on one side the principle of authority, the cornerstone of the scholastic method, which was based solely on the opinions of writers and on comparison of texts, while in reality 'human authority' is devoid of any value that overrides 'the effects of nature, which is relentlessly deaf to our vain desires.' It also struck the dominant culture 's mode of expression, which Galileo deemed 'vain wandering through a dark labyrinth.' Common language is not the one proper to natural philosophy, because the book of the universe is 'written in mathematical language', and the letters of this language are 'triangles, circles and other geometric figures.'

 

Considering, however, that 'concentration on rigorous geometric demonstrations is too dangerous a venture for those who do not know how to manage them well', the scholars of the Aristotelian tradition, ignorant of mathematics, had always taken refuge in 'limitations', distinctions', 'distortion of words' and reckless, tortuous reasoning which had brought anything but progress to the knowledge of nature. Galileo saw the linguistic acrobatics of his opponents as a means of eluding the inevitability of demonstration, the only way that led, concisely and immediately, to a definitive distinction between the true and the false. He elaborated this in his own way with one of his most elegant images: 'In the necessary demonstrations... one must, in brief words and in the first assault, become either Caesar or nothing.' Apart from his mastery of the mathematical language, he was second to none in his skilled use of ordinary language.

 

Within a few years, the tactics of the Jesuits, in the face of such science, showed themselves for what they were, raising the spectre of prison whenever theory could not come to their aid. In 1626 Father Grassi, in yet another of his replies, isolated a passage from The Assayer in which Galileo described as intrinsically proper to bodies only certain characteristics such as motion, figure, number, dimension (that is, everything that can be measured), which, he maintained, depended on the activity of 'a multitude of tiny bodies' of which matter is composed. The other characteristics, such as taste, colour, and odour, have value only for the sense organs that perceive them, being nothing in relation to the bodies and their physical properties, 'pure names', as Galileo said. But 'it is commonly affirmed that, in the Host, heat, flavour and such, persist', commented Father Grassi, continuing, 'We must thus infer that Galileo maintains that heat and taste do not exist in the host. The soul is horrified at the very thought!' With this coup de main the discussion was shifted from the scientific level, where the confrontation was unequal, to the theological one, where confrontation was inadmissible. And Rome was now haunted by the spectre of prison. The Inquisition began to examine the work of Galileo, who only a few years before had obtained the imprimatur without difficulty, to identify all the points where his stealthy atomism might have violated the Catholic doctrine of the Eucharist and the dogma of transubstantiation.