Bruno and the Extra-Terrestrials

Sunday, July 1st, 2012 | Greg Dawes | 2 Comments

Giordano Bruno (Livre du recteur, University of Geneva, 1578)

The SETI League, which is dedicated to the search for extra-terrestrial intelligent life, each year offers an award in honour of Giordano Bruno (15481600).

Bruno was, notoriously, burned to death in the Campo dei Fiori in Rome, after eight years of imprisonment and condemnation by the Roman Inquisition. One of the judges who condemned him was the learned Jesuit, Robert Cardinal Bellarmine, who would later play a prominent role in the Galileo affair (and who is now Saint Robert Bellarmine).

So why should a sixteenth-century heretic be associated with the search for extra-terrestrial life, a search that involves thousands of computers scanning the electromagnetic spectrum for that longed-for (or perhaps dreaded) signal, that suggests we are not alone in the universe?

An image from Copernicus's "De Revolutionibus"

Bruno, along with Galileo, was one of the first defenders of Copernican cosmology. Indeed he seems to have been the first to note that the anonymous preface to Copernicus’s De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres) was not written by Copernius himself. We now know that preface to be written by the Lutheran theologian Andreas Osiander. It offers an instrumentalist interpretation of Copernicus’s cosmology, arguing that his picture of the universe should not be understood as a description of the way it actually is, but as a mere instrument for calculating heavenly movements. Along with Johannes Kepler (1571–1630) and Galileo (1564–1642), Bruno denied that this was Copernicus’s intention and held to a realist interpretation of his cosmological scheme.

A 1483 copy of Lucretius's work, produced for Pope Sixtus IV.

But in many respects Bruno went beyond Copernicus. He followed the Roman poet Lucretius (ca. 99–55 BC), as well as some late medieval thinkers, in affirming the existence of a universe that is infinite in extent. While Bruno coupled this with a defence of Copernican cosmology, he realized that such an idea rendered moot debates about the centre of the universe. As Lucretius had already written in his De rerum natura (I,1070), “there can be no centre to that which is boundless” (medium nil esse potest infinita). In his De la causa, principio et uno (Fifth Dialogue), Bruno expresses a similar idea with a paraphrase of the words of Nicholas of Cusa (1401–64). One can affirm with equal truth, he writes, that “the centre of the universe is everywhere, and the circumference nowhere” (il centro de l’universo è per tutto, e che la circonferenza non è in parte alcuna) or that “the circumference is everywhere, but the centre is nowhere” (la circonferenza è per tutto, ma il centro non si trova).

Of more interest to the SETI League is the fact that Bruno believed this infinite universe to be populated by an infinite number of worlds, in the sense of planetary systems orbiting other suns. He claimed that these worlds were inhabited by creatures like, or even superior to, ourselves.

Such ideas sound very modern. But should we regard Bruno as a pioneer of modern science? This idea was vigorously contested by Frances Yates, who in her 1964 book Giordano Bruno and the Hermetic Tradtion, argued that Bruno is better thought of as a Renaissance magus. More recently, Hilary Gatti, in her book Giordano Bruno and Renaissance Science, has tried to reforge a link between Bruno and the new natural philosophy of the sixteenth and seventeenth centuries. But even Gatti is loathe to describe Bruno as a practitioner of the new science. He is merely “a friend and supporter of the new science,” who, while supportive of aspects of that new knowledge, is also “deeply suspicious of some of its outcomes and consequences.”

Galileo Galilei in 1636 (Portrait by Justus Sustermans)

What’s important to note is that Bruno does not reason in the same manner as, say, Galileo, who in a letter to Fortunio Liceti in 1639 admitted that he could not decide if the universe is infinite or bounded. Bruno has no such hesitations. As Gale Christianson writes (Science Fiction Studies March 1976), Bruno “soared into the metaphysical realm unencumbered by the ballast of scientific thinking.”

In particular, Bruno’s belief in an infinite universe populated by a plurality of worlds is not based on any empirical data. In fact, he believes there could be no empirical evidence for such a claim. As he writes near the beginning of De l’infinito universo, “no corporeal sense can perceive the infinite. None of our senses could be expected to furnish this conclusion; for the infinite cannot be the object of sense-perception” (non è senso che vegga l’infinito, non è senso da cui si richieda questa conchiusione; perché l’infinito non può essere oggetto del senso).

Rather than being based on empirical evidence, Bruno’s conviction is based on a theological principle. It is based on the idea that an infinite creator could not do anything other than create an infinite world. To suggest that God would create a finite universe is to accuse the Creator of being miserly or envious (invidioso), since he would be refusing to share his own goodness (De l’infinito universo First Dialogue). It follows, as Bruno writes, that “we insult the infinite cause when we say that it may be the cause of a finite effect” (infinita causa injuriose finiti dicetur effectus causa) (De immenso et innumerabilibus I, 9).

It is deeply ironical that Bruno, who was put to death by the Church, argued for a revolutionary scientific conclusion on theological grounds

So is Bruno a pioneer of modern science? In some of his conclusions, yes, perhaps he is. But in the manner in which he is reasoning he certainly is not. In fairness to the SETI League, they also recognize this fact. While naming an award after Bruno, they have also posted a critical essay by Richard Pogge, suggesting that Bruno’s thought has little to offer the modern searcher for extra-terrestrial intelligence.

There is, of couse, a lesson to be learned here. Before we describe a thinker as a precursor of some modern ideas, we need to examine, not merely the conclusions at which he arrived, but the ways in which he arrived at them. This may involve styles of reasoning that are far removed from those we would consider scientific.

Astronomy and Astrology

Tuesday, June 5th, 2012 | Greg Dawes | No Comments

Greg Dawes writes …

One often reads, at least in popular works, that pre-modern European thinkers made no distinction between astronomy and astrology. A Wikipedia article, for example, begins by claiming that “astronomy and astrology were archaically one and the same discipline (Latin: astrologia), and were only gradually recognized as separate in Western 17th century philosophy.” Another website claims that “astronomy and astrology cannot be separated in the Middle Ages and the early modern period,” while a third asserts that in the early university faculties, “astronomy and astrology were not separate,” but were “indivisible sciences.”

Galileo Galilei in 1636 (Portrait by Justus Sustermans)

But is this correct? It is true that in medieval and early modern thought astronomy and astrology were closely associated. Furthermore, many authors of this time regarded both as reliable sources of knowledge.  Indeed astrology continued to be taken seriously well into the seventeenth century.  As H. Darrel Rutkin has noted (Galilaeana (2 [2005]: 107–142), early seventeenth century mathematicians, even those employed by universities, were often called on to cast horoscopes. No less a figure than Galileo seems to have taken astrology seriously, casting horoscopes not only when he was requested to do so, but also, for example, to predict the characters of his two daughters.

Nonetheless, it is wrong to say that pre-modern European thinkers made no distinction between astronomy and astrology. There was, first of all, a long tradition of scepticism regarding what is known as “judicial” astronomy, with its claims to be able to predict the course of an individual’s life. This tradition dates from Cicero’s De divinatione and continues with the work of St Augustine. It finds a late medieval expression in the criticisms of Nicole Oresme (1320–82) and reaches its high point in the work of Pico della Mirandola (1463–94). These writers rejected judicial astrology, but there is no reason to think they were rejecting astronomy. They offered no arguments against a mathematical treatment of heavenly movements, the science which had found its fullest expression in Ptolemy’s Almagest.

A sixteenth-century edition of a thirteenth-century work on Ptolemaic astronomy. (Photograph by Wolfgang Sauber)

Even among those who approved of astrology, a distinction was made between astronomy and astrology. It can be found, for instance, at the very beginning of the work known as the Speculum astronomiae, the “mirror of astronomy,” generally attributed to Albert the Great (ca, 1200–80). While using the same word (astronomia) for both astronomy and astrology, it begins by making a clear distinction between them. “There are two great wisdoms,” it begins, which go by this name: the first has to do with the configuration and movements of the heavens, while the second has to do with “the judgements of the stars.”

Still more interesting is a second work, the De fato, which dates from the same period. This not only makes the distinction, but spells it out in terms of the differing kinds of knowledge that are involved. The passage in question is responding to the objection that astrological prediction is not a science: what demonstrable connection is there, the objector asks, between (for example) the position of the moon in Leo and the type of clothing one should wear? The author’s response is to note that

as Ptolemy says, in astronomy we must distinguish two parts: the first concerns the positions of the superior bodies, their measures and their passions; this part of astronomy can be reached through demonstration. The other part concerns the effects of the stars in inferior things, effects which are received differently in these mutable objects [qui in rebus mutabilibus mutabiliter recipiuntur]. Thus, the second part can only be reached through conjecture. … From conjectures, which derive from mutable data [cum sit ex signis mutabilibus], comes a mental attitude endowed with less certainty than science or opinion. (De fato 4.7, translation by Paola Zambelli)

As the reference to Ptolemy suggests, the author considers that he is doing nothing new in making distinctions of this kind. They are already ancient, going back to the work of the great second-century astronomer, who wrote one work, the Almagest, on what we would call “astronomy,” and another, the Tetrabiblos, on astrology. The latter begins by making just the same point.

Of the means of prediction through astronomy, … two are the most important and valid. One, which is first both in order and in effectiveness, is that whereby we apprehend the aspects of the movements of sun, moon, and stars in relation to each other and to the earth, as they occur from time to time; the second is that in which by means of the natural character of these aspects themselves we investigate the changes which they bring about in that which they surround. (Ptolemy, Tetrabiblos I.1, Loeb translation)

What about the early modern period? Was the same distinction made then? It seems that it was, at least by some thinkers. I have already noted that Galileo does not deny the possibility of astral and planetary influences on human affairs. Indeed, his practice of astrology assumes it. But he does deny that it can produce the kind of certain knowledge that he, like his predecessors, regarded as essential for a science. Again, H. Darrel Rutkin provides evidence of this, drawing our attention to a letter of 1633 in which Galileo comments on the views of Jean-Baptiste Morin (1583–1656). Galileo criticises Morin, not for believing in astrology itself, but for believing that astrology could attain to certainty and for placing it at the head of the sciences.

So do premodern European thinkers make a distinction between astronomy and astrology? Yes, they do. Is their distinction identical with ours? No, for the most part it is not. But it would be wrong to overlook the way in which late medieval and early modern thinkers distinguished between what they considered differing forms of knowledge and the degree of certainty to which each could aspire.