THE PONTIFICAL ACADEMY OF SCIENCES Plenary Session on PREDICTABILITY IN SCIENCE: ACCURACY AND LIMITATIONS 3-6 November 2006 Introduction p.3 Background Note p.3 Programme p. 5 Commemoration p.7 Abstracts p.8 Memorandum p. 11 14 EM AD I A C S A C I A E I N C T I I F A I R T V N M O P VATICAN CITY 2006 As I wrote in the encyclical Deus Caritas Est, at the source of Christian existence – and thus also at the origin of our witness as believers – is not an ethical decision or a great idea, but the en- counter with the person of Jesus Christ, ‘who gives life a new hori- zon and with this its decisive direction’ (n. 1). The fecundity of this encounter manifests itself in a particular and creative way in the current human and cultural context as well, above all in relation- ship with the reason that has given rise to the modern sciences and to the related technologies. A fundamental characteristic of the latter of these is, in fact, the systematic employment of the tools of mathematics in order to work with nature and to place its immense energies at our service. Mathematics as such is a creation of our intelligence: the correspon- dence between its structures and the real structures of the universe – which is the premise for all the modern scientific and technologi- cal developments, already formulated explicitly by Galileo Galilei with the famous assertion that the book of nature is written in mathematical language – arouses our admiration and raises a great question. It implies, in fact, that the universe itself is structured in an intelligent manner, in such a way that there exists a profound correspondence between our subjective reason and reason as objec- tified in nature. So it becomes inevitable to ask if there must not exist a single originating intelligence, which would be the common source of both the one and the other. And so it is reflection on the development of the sciences which itself brings us back to the creator Logos. This reverses the tenden- cy to give primacy to the irrational, to chance and necessity, bring- ing back into focus our intelligence and freedom. On these bases, it again becomes possible to expand the spaces of our rationality, to reopen it to the great questions of truth and goodness, to bring to- gether theology, philosophy, and science, in full respect for their proper methods and their reciprocal autonomy, but also in the awareness of the intrinsic unity that holds them together. This is a task that stands before us, a fascinating adventure in which it is worthwhile to exert oneself, in order to give a new im- pulse to the culture of our time and to restore the full citizenship of Christianity within it. The programmatic address from Pope Benedict XVI to the National Con- ference of the Church in Italy, 19 October 2006. 2 Predictability in Science: INTRODUCTION Accuracy and Limitations WERNER ARBER & NICOLA CABIBBO n its last two business meetings the PAS important. It is not our role to debate on prophe- Council discussed several alternative topics cies. Predictions on a scientific basis can be I that had been proposed for the next Plenary more or less accurate and have in most cases Session of the Pontifical Academy of Sciences in their intrinsic limitations. We therefore consider November 2006. On the basis of these delibera- expressing this in a subheading. The proposed tions the Council has chosen the theme of ‘Pre- theme would then read as follows: ‘Predictabili- dictability in Science’. This theme is situated at ty in Science: Accuracy and Limitations of Pre- the interphase between fundamental science and dictions based on Scientific Knowledge’. its practical applications to the benefit of human We expect that all scientific disciplines can beings. We will welcome contributions on scien- contribute with selected examples to a wide de- tific predictions of impending dangers, such as bate on scientific predictions and their relevance earthquakes, on the outlook for climate change, to society. Thereby, the awareness of natural lim- on the analysis of nuclear and other technolo- itations that are inherent to many predictions gies, in the role of prediction in the medical sci- plays an important role and it can insure the ences, and on many other scientific predictions trust in science in interactions between science and modelling approaches that frequently also and the civil society. The distinction between cer- have their applications with impact on cultural tainties and uncertainties has since long been and socio-political developments. made by many scientists presenting scientific According to Webster’s dictionary the word knowledge, theories and models on natural de- prediction has two meanings: (1) a predicting or velopments. A candid discussion on this theme being predicted, and (2) a prophecy. Obviously, by the Pontifical Academy of Sciences can rep- only the first meaning applies to our proposed resent a clarifying view for both the scientific theme. Therefore the word science in the title is community and the general public. BACKGROUND NOTE M. GOVIND KUMAR MENON he idea behind this meeting is that a great animals to people, all figure in societal discus- deal is done within science which only sci- sions these days. In most of these cases, the is- T entists would deal with; but there are, in- sue is that whilst there is a very good scientific creasingly, many other aspects of science which basis at the initial stages, as one proceeds down have public implications, that figure extensively the line, to predictions of relevance to society, in the audiovisual and print media. With regard many aspects such as complexity, non-equilibri- to the latter, a public understanding of accuracy um phenomena, chaos and the like come in in- and uncertainty in the predictions, arising from troducing uncertainties in the predictions. scientific knowledge, become important. Thus, one has clear-cut observations on the Most of these aspects of general public inter- carbon dioxide concentrations in the atmos- est relate to complex phenomena; and some re- phere and how they have increased with time. late to ethical issues that could have political, so- One knows that carbon dioxide is a greenhouse cial and economic ramifications. For example, gas; and there are also other greenhouse gases. issues relating to weather prediction, climate The increase in their concentrations will result change, prediction of earthquakes, the possibili- in a greenhouse effect, which will cause a rise in ty of major natural disasters such as an asteroid global temperature. Sources, pathways, sinks hitting the earth, pandemics from the sars virus, and budgets at each stage will define what ulti- bird flu and the like that could cross over from mately happens. 3 Predictability in Science. Accuracy and Limitations Background Note These will have implications on sea levels, For example, what is the price to be attached to change in climate patterns, extreme events in the ecological services provided by water? precipitation, availability of water etc. At each Today, there are very significant advances in stage there is a greater degree of uncertainty, modelling capabilities and one needs to evaluate and an increasingly poorer predictability and the accuracy and limitations in prediction based lack of consensus. Society gets confused and on these techniques. While it would be possible begins to doubt whether scientists know what with increasing knowledge and capabilities to they are talking about e.g. the fun many have have predictions in many areas, these would nev- at the expense of meteorologists. When one gets er be 100% correct, and one would have to live to the human dimensions of global change, be- with uncertainty. In fact, it is this uncertainty havioural change etc come into the picture, e.g that makes further development of science excit- involving economics, psychology and social be- ing, because there is so much more to know and haviour, human dislike for measures that de- to understand. mand lifestyle changes. This is the type of prob- However, there is also the question of deci- lem dealt with by the Inter-Governmental Pan- sions that have to be taken by governments and el on Climate Change. society at any point in time for which advice The above somewhat lengthy real life exam- from the scientific community is called for. This ple was only to illustrate the nature of the prob- would bring out the importance of the precau- lem because the public generally assumes that tionary principle, to avoid getting into a situa- science can be certain and give accurate answers. tion that might lead to catastrophic events. There is then the possibility of climate engi- It is felt that the intrinsic issue of scientific neering to reduce greenhouse effects. But this uncertainty, particularly in complex, non-equi- could raise ethical issues related to tampering librium systems, and limits of predictability with a natural system and predictability of the need to be discussed from the viewpoint of vari- hazards involved in this. ous angles. It is felt that apart from natural sci- There is the issue relating to genetically mod- entists it would be important to have some dis- ified organisms and their large scale use in soci- tinguished thinkers who deal with dimensions ety. There are many who are opposed to this on that human society is normally concerned with the grounds that one would not know what e.g. economic, social and behavioural aspects al- might ultimately happen; and more particularly so participate in this plenary session. This is be- in relation to the environment. cause many of these areas are characterised by There is the broad area of environment and non-equilibrium complex situations and are al- ecology where society seldom looks at the price so increasingly using the techniques developed being paid for certain pathways of development.