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Piecewise versus Total Support: How to Deal with Background Information in Likelihood Arguments
- Benjamin C. Jantzen
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- Philosophy of Science / Volume 81 / Issue 3 / July 2014
- Published online by Cambridge University Press:
- 01 January 2022, pp. 313-331
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- July 2014
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The use of the Law of Likelihood (LL) as a general tool for assessing rival hypotheses has been criticized for its ambiguous treatment of background information. The LL endorses radically different answers depending on what information is designated as background versus evidence. I argue that once one distinguishes between two questions about evidentiary support, the ambiguity vanishes. I demonstrate this resolution by applying it to a debate over the status of the ‘fine-tuning argument’.
11 - The modern likelihood argument
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 05 June 2014
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- 27 February 2014, pp 170-188
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Probability, likelihood, and Bayes’ Theorem
The first argument we’ll consider from the modern era is a special sort of inference to the best explanation for which the vague term ‘best’ is given a rigorous formulation in terms of something called the ‘Likelihood Principle’. To understand this version of the design argument, we need to be clear about some basic features of probability, so we’ll begin this chapter with a quick review.
While it is easy to present the mathematical theory of probability – the probability calculus – it is difficult to give an account of just what probability is. This is because there are many different processes or features of the world that are well modeled by the probability calculus, just as many things can be modeled with algebra or geometry. There is likely no one thing that probability is really about, and in our discussion we’ll see the calculus of probability applied in at least two different ways. On the one hand, probability describes processes that we think of as genuinely or inherently chancy – processes like the flip of a coin, the spin of a roulette wheel, or the decay of an atom. We tend to think that in at least some of these cases, there is no way in which the world must turn out – the coin could come up heads or tails – but the patterns in which such events are found to occur is well modeled by probability theory. The calculus lets us know what to expect. On the other hand, the probability calculus is good at modeling the ways we should change our beliefs about the world when we lack total information, at least if we want to be rational in certain ways. In this sense, probability is a measure of our degrees of belief. I won’t try to argue for any one interpretation of the probability calculus (in part because I don’t believe there is a unique interpretation), and an examination of the difficult questions surrounding the notions of randomness, chance, and ‘degrees of belief’ will lead us too far astray. Instead, I’ll motivate the parts of the mathematical theory we’ll need with an intuitive example involving a chance process. Once we have the math down, I won’t stipulate an interpretation unless it is relevant.
4 - Medieval arguments
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 05 June 2014
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- 27 February 2014, pp 47-57
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Summary
Introduction
Our aim in scrutinizing the historical literature is to identify and assess the major forms of design argument. In the last chapter, we considered the design arguments available as of about 100 BCE, all of which were defended by the Stoics at one time or another. Now we’re going to glide over the next fifteen centuries or so, stopping only to scrutinize a single argument from the High Middle Ages. The reason for our haste is that the development of design arguments largely stagnated from the time of Cicero until the scientific revolution. This wasn’t for lack of interest in things divine. Rather, it is a consequence of historical forces that temporarily suspended the broader project of natural theology – the attempt to address questions concerning the existence and character of God on the basis of reason and experience. These historical forces center on Rome. In the fourth century CE, the Roman empire in effect converted to Christianity following the Emperor Constantine. As the last Roman emperor to rule over a united empire, Constantine moved the official capital to Byzantium, well east of the empire’s traditional seat of power in Italy. Not long after his death, the empire permanently split in two, and the two fragments followed very different intellectual trajectories with rather different perspectives on design arguments. For this reason, the intellectual history of design arguments through the following centuries is best told in two parallel stories, one for the Christian West and one for what would ultimately become the Islamic East.
Medieval arguments from the Islamic East
The eastern fragment of the Roman empire kept Greek philosophy and the Stoic interest in design arguments alive. Centered in Constantinople, it evolved into what we moderns call the Byzantine empire, which lasted until the fifteenth century CE. Though romanized, spoken Greek persisted there, and this doubtless helped to preserve Hellenic philosophy. It was from the Byzantine world that Greek philosophy made its way into Islamic culture. In the mid seventh century CE Arab armies began spreading Islam by force. In 641 CE they captured the city of Alexandria, whose vibrant intellectual life had survived the collapse of the Roman empire. This city’s rich collection of Greek and Roman philosophy – most prominently the works of Plato and Aristotle – thus found their way into Arabic translation, and provided a foundation for the development of Islamic philosophy.
List of figures and tables
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 05 June 2014
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- 27 February 2014, pp ix-xii
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19 - Conclusion
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 27 February 2014, pp 311-315
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Recapitulation
Most of the design arguments appearing in this book can be viewed as variations on a handful of themes already present in Stoic thought by the first century BCE. I’ve been calling these the argument from order, the argument from purpose, the argument from providence, and the argument by analogy (see Chapter 3). Though I often refer to them in the singular, each is really a family of arguments united by a common schema, a logical form with placeholders for premises that can be filled in a variety of ways. So to be more precise in this review, I’ll refer to the arguments from order, etc.
The arguments by analogy assert that, given all the ways in which the universe resembles a machine, we should conclude that it also resembles a machine in having a designer. This family of arguments was brought into its sharpest focus and then undermined by David Hume (see Chapter 7). The arguments from purpose appeal to natural phenomena, especially the ways in which living things are adapted to their environment, that are supposed to self-evidently exhibit purpose. In Chapter 10, we saw that we must disambiguate senses of ‘purpose’ to avoid begging the question. After all, what we are trying to establish is whether any portion of the natural universe was purposefully arranged by a designing intelligence. But when this is done the argument collapses – it is not the case that the sort of ‘purpose’ which can be observed in the natural world entails or even suggests design.
Frontmatter
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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8 - Paley
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 27 February 2014, pp 118-135
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Who was William Paley?
In the modern era, there is no bigger name in natural theology than that of William Paley. He ended Cicero’s nearly 2,000-year reign as the principal authority on the subject. Prior to 1800 CE, Cicero was widely cited and widely emulated. Even Hume composed his critique as a dramatic dialogue that closely imitated Cicero’s De natura deorum. By the 1830s, however, Cicero had moved to the footnotes and the work of William Paley had become the most ubiquitously cited, referenced, and quoted. There is little in Paley’s biography to foreshadow this intellectual upset. By all accounts his life was uneventful. In 1743, he was born into relative comfort as the eldest son of the Reverend William Paley. The younger William was regarded as a bright but clumsy young man, fond of fishing. When he exhausted the resources of the local school, he was sent off to Cambridge University at the tender age of 16. There, like his intellectual forebears John Ray and William Derham, he was ultimately ordained in 1766.
When he was later elected fellow of his old Cambridge college, Paley returned to teach. It was as an instructor in moral philosophy that he began to stand out. His lectures were innovative and well received, and he drew upon them to write his first book, The Principles of Moral and Political Philosophy in 1785. The book attempts to ground a utilitarian ethics upon the will of God and was a great success. It was followed by another, Horae Paulinae, in which Paley tries to authenticate the narratives of the New Testament, in particular the story told by the letters attributed to Paul. It is somewhat ironic that his strategy in that book is to argue that similarities among the various biblical texts are not the product of design. This book was succeeded by Evidences of Christianity – a broader attempt to marshal historical evidence in favor of the faith. It was so highly regarded that by the time a young Charles Darwin was a student at Cambridge, it had been made part of the standard curriculum.
3 - Arguments from antiquity
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 27 February 2014, pp 29-46
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The emergence of design arguments
We’ll begin our historical survey of design arguments in the first century BCE. This choice is somewhat arbitrary, since by that point in history, what we would recognize as a design argument had been around for centuries. But it was around this time that Cicero wrote his De natura deorum, the oldest surviving manuscript to gather together and assess the full crop of ancient design arguments. This work represents the earliest point at which the handful of arguments we will follow over the next two millennia were indisputably in play, and so it makes a natural starting point for studying design arguments. Nonetheless, it is worth glancing back into the earlier days of design arguments – and of philosophy itself – before we go forward with our survey.
It would take another book altogether to trace the crystallization of recognizable design arguments from the rich brine of early philosophy. To begin with, the emergence of design arguments had to wait for a particular combination of philosophical views to develop. This was not for lack of conviction in the existence of gods or divine intelligence. Rather, the earliest known attempts at systematic, scientific explanation of the world (as opposed to mythic or religious ones) simply assumed that intelligence like ours is the dominant mechanism in the physical world – everything was considered animate to one degree or another. Particularly for the scientifically minded Milesians, early attempts at a workable physics focused on the search for ‘principles’, the primary causes of all structure and change. For instance, Thales of Miletus declared that the principle is water. By this he seems to have meant that water is the original substance of the world, and all subsequent physical features of the world can be accounted for on the basis of the properties of water and its changing states. If we are to believe Aristotle, Thales also said that “all things are full of a gods.” That seems an odd thing to say after offering a sort of physical theory of the world, but it is characteristic of early accounts. It is a bit of a caricature, but such accounts understood living intelligence to be a pervasive force which could be used to explain the structure of the world and our experience of it.
2 - Preliminaries
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 27 February 2014, pp 18-28
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Summary
Overview
In Chapter 1, we considered some of the intuitions that suggest design in the natural world. But intuitions alone are a thin justification for belief. This book is concerned with the careful, rational justification that only a good argument can provide. And history has provided plenty. Over the past 2,000 years, a great variety of arguments have been offered, each of which tries to establish that at least part of the world has been designed. But before we can capitalize on these arguments – before we are in a position to sift and weigh them, eliminating the weak and isolating the strong – we have to do a little stage setting. We need to develop a vocabulary for referring unambiguously to the parts of an argument, and for characterizing the different kinds of argument we come across. Not every sort of argument – even when successful – offers the same degree of confidence in its conclusion, and we need to be able to recognize the difference. Some of this work will be left to later chapters where fresh terminology is introduced as it is needed. In this chapter, we’ll consider a few simple design arguments based on the case studies of Chapter 1 and introduce just enough technical jargon to get us through our first set of historical arguments.
Arguments and their parts
Consider the following argument for the existence of God based on features of the parasitic wasps we considered in case study 3 of the last chapter:
Example 1
The egg-laying ovipositor of the wasp Megarhyssa is built just right to function as an efficient drill. An efficient drill could not form by chance. Since every structure is the result of design or chance, some intelligent being must have intended for the wasp to have such a drill. Therefore, there exists a being – call it God – who designed Megarhyssa.
14 - What is complexity?
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 27 February 2014, pp 226-239
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Life: a classic example of ‘complexity’
The boundaries are hazy, but there does seem to be a genuine, objective distinction between living and non-living things. Unlike inanimate objects, living things reproduce, metabolize, and evolve. They are also vastly different in structure from non-living things. Living things tend to be highly organized at any given level of description and so differ from objects like stones, lakes, and volumes of gas which tend to have uniform or ‘random’ structures: Peer at a stone through a microscope and you’ll find a jumble of randomly oriented mineral crystals. Look closer and you’ll find the interiors of these crystals to be fairly uniform. Examine instead a cross-section of a sheep’s eye and you’ll discover intricate layers of tissue. Look closer at any one of these and you’ll discover cells, each of which contains a visible nucleus. Use the right tools to look even closer and each of these cells will reveal myriad structures like mitochondria. You will discover fresh structure in the eye all the way down to the molecular level. So unlike a rock, the structure of an organism is highly layered. Like the rock, however, the structure of an organism at any one level of description is often asymmetric. Though from the outside humans are bilaterally symmetric, on the inside many of our organs – like the liver and pancreas – are not arranged according to any particular symmetry. Because of this asymmetry, living things are easily distinguished from such things as snowflakes, crystals, and man-made gears.
17 - Fine tuning I: positive arguments
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 27 February 2014, pp 272-290
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A cosmic conspiracy?
In 1979, a curious paper appeared in the pages of the eminent scientific journal Nature. The paper was unusual because it did not report on novel experimental findings. It did not offer a new theory or explanation of known phenomena. It did not even survey the current status of a developing branch of science as other ‘review articles’ in the journal typically do. Instead, it argued for a long list of coincidences of two kinds. First, there are the connections between different branches of physical science. As the paper’s authors, B. J. Carr and M. J. Rees explain, “[t]he structure of the physical world is manifested on many different scales, ranging from the Universe on the largest scale, down through galaxies, stars and planets, to living creatures, cells and atoms … Each level of structure requires for its description and explanation a different branch of physical theory, so it is not always appreciated how intimately they are related.” They set out in part to exhibit this intimate connection by demonstrating how most of these disparate ‘natural scales’ described by different theories are all determined by a shared handful of dimensionless parameters. In fact, most of their examples involve just three parameters: the electromagnetic fine-structure constant (α), the gravitational fine-structure constant (αG), and the electron-to-proton mass ratio (me/mp). So, for instance, the authors provide a simple physical argument for the fact that most stars have a mass in a range between 0.1 and 10 times that of our Sun. This range of possibility is itself dictated by the parameter αG. Of course, that parameter might have had a different value, at least as a logical possibility. In that case, the range of masses computed would be different. So whatever value αG has, physical processes of the sort operating in our universe guarantee that stars form only in a particular range, but what that range is could be different. Similarly, the authors argue that the size of a typical atom is dictated by the value of α – the bigger α is, the smaller a typical atom is.
Contents
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 27 February 2014, pp vii-viii
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16 - A brief survey of physical law
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 27 February 2014, pp 259-271
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Viewing natural laws as artifacts
Most of the design arguments we’ve encountered focus on parts of the universe and argue that this or that part of the world could only have come to be the way it is because some intelligent agent helped make it that way. As we turn to consider the phenomena of so-called ‘cosmic fine tuning’, we will find that the focus shifts to the universe as a whole. Rather than worry about properties of things in the world, a fine-tuning argument for the existence of God emphasizes properties of the universe. Typically, the proponent of such an argument looks to the form of the particular physical laws thought to govern the unfolding of the universe, and in particular to a set of ‘constants’ that feature in these laws. The relevant intuition is that the laws would not have the form they do were it not for the will of an intelligent agent. In a sense, fine-tuning arguments attempt to establish that the very laws which shape and govern the universe are artifacts.
In order to assess the plausibility of fine-tuning arguments, it will help to have some idea of what is meant by a ‘physical law’ and what laws in particular are currently thought to govern our universe. This chapter presents a survey of the major physical laws invoked by design arguments. I won’t attempt here to give a philosophical characterization of what a law is – we’ll worry about that later. Rather, my aim is to present the laws that will serve in key premises in the next two chapters, and to do so in a manner accessible to the non-specialist. The reader who is comfortable with the basics of modern physics can profitably skip this chapter. Similarly, the reader who wishes to avoid all technicalities can leap ahead to Chapter 17 and still be able to follow the gist if not the details of the fine-tuning arguments. For everyone else, I offer this guide to modern physics in three short acts.
9 - Darwin
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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Why dwell on Darwin and his theory of natural selection?
In this chapter we examine a scientific theory – Charles Darwin’s theory of evolution by natural selection. This might seem a like a detour. After all, a scientific theory is neither a design argument, nor a direct criticism of a design argument. However, there are two reasons that an examination of Darwin’s work is essential. First, Darwin explicitly casts his theory of the origin of biological species and their complex adaptations as a competitor to ‘special creation’, the default mode in which God was presumed to have populated the world with living things. Thus, an argument for evolution by natural selection is an argument against at least one sort of conclusion supported by design arguments. Second, Darwin’s theory presents an alternative mechanism for generating the sort of order that appears in the argument from order. It thus has a direct bearing on the plausibility of one of the most popular and durable design arguments with which we’ve met so far.
The life of Darwin
Charles Darwin shares a birth date with Abraham Lincoln: February 12, 1809. Aside from being a curious coincidence, this fact helps to situate Darwin historically. Darwin’s early life encompassed the rise and fall of Napoleon and the bloody wars that accompanied both. He witnessed the culmination of the Industrial Revolution, and from 1830 to 1846 lived through an era of electoral and governmental reform in the British Isles. Darwin’s thought was surely influenced by these events and by the profound demographic, intellectual, technological, and ideological shifts that accompanied them in nineteenth-century England.
Preface
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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Preface
This book is a critical survey of design arguments, attempts to infer the existence of a God or gods by demonstrating the likely role of intelligence in shaping the world of experience. By critical, I do not mean polemical. What follows is not an attempt to dismiss design arguments as categorically misguided or ill-conceived. Nor is it a religious apologetic. Rather, it is intended to be a neutral philosophical reconstruction and analysis of the entire field of design arguments advanced from the rise of Western philosophy in ancient Greece to the present day.
The treatment of this material is introductory in a couple of ways. As with any introduction to a field of study, I have sacrificed some depth in favor of breadth in order to give the reader a coherent picture of the entire landscape of the design debate. My aim is in part to provide a synopsis of a long philosophical conversation so that someone interested in working on the philosophical puzzles surrounding design arguments can jump right in. The book does not assume that the reader is familiar with the jargon of academic philosophy or has had any formal training in the analysis of arguments, and so can serve as the basis for an introductory course in philosophy or critical thinking.
10 - Loose ends
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 27 February 2014, pp 153-169
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Summary
Overview
In our survey of the first twenty centuries or so of design arguments, we covered a lot of ground. In the process, many issues worth considering were raised but quickly set aside. This chapter collects a number of these issues together and gives each due consideration. The reader in a hurry can skip this motley collection without losing the thread of debate. But for those with nagging questions about the idea of purpose in nature, how much natural theology can establish about the attributes of God, or the connection between William Paley and Bernard Nieuwentyt, what follows will be of interest.
Purpose in nature
In Cicero’s dialogue De natura deorum, there appears an argument that rests on the observation of ‘purpose’ in the universe. This argument resurfaced centuries later in the great compendia of natural history such as Derham’s Physico-Theology. Despite the longevity of this sort of argument, we quickly passed over it with little scrutiny when it came up in our survey. It’s time we rectified that oversight.
7 - Hume
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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- 27 February 2014, pp 99-117
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Summary
Overview
Ask a modern philosopher about Hume and the design argument, and there’s a good chance you’ll hear this story: the design argument is an argument by analogy that compares the universe to a machine and concludes that, like a machine, the universe has a designer. Of course, that designer is supposed to be God. For a brief period of time following the scientific revolution, this argument flourished. But in the late eighteenth century, a philosopher named David Hume unmasked the design argument as a hopeless failure. Those that continued to defend the argument after Hume, most famously a fellow named William Paley, were merely propping up a corpse – the design argument had already died at the tip of Hume’s pen.
As we will see in this chapter and the next, most of this tale is false. While Hume did in fact devastate the argument by analogy, it was largely an argument of his own creation. There are other types of design argument that, while seriously challenged by Hume, are not obviously defeated by him. In fact, Hume provides some of the most important rebuttals to his own critique, rebuttals that others like Paley will use to keep design arguments alive. But we’re getting ahead of ourselves. Let’s first take a moment to introduce Hume and the book that had such an impact on natural theology.
1 - Introduction
- Benjamin C. Jantzen, Virginia College of Technology
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- An Introduction to Design Arguments
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What this book is about
Broadly speaking, we human beings use two conceptual schemes or ‘paradigms’ to explain the world in which we find ourselves. In the ‘teleological paradigm’ natural events are explained in terms of the same sorts of purposes, means, and goals we use to explain our own behavior. Within the ‘naturalistic paradigm’, the world is explained in terms of natural laws and mindless processes. The naturalistic paradigm has been enormously successful. As an underlying framework for science, this way of approaching the world has yielded a vast knowledge of natural phenomena, as well as the technology which distinguishes our modern way of life from all that came before. The teleological paradigm on the other hand is ancient and deeply intuitive. The oldest human accounts of nature were made from this perspective. The creation stories of cultures around the world – from the Babylonian account in which Merodach fashions the world from the corpse of the great Mother dragon Tiamat, to the biblical story of Genesis – are examples of teleological explanations. While such explanations have been largely displaced by appeals to natural law, one product of the teleological paradigm continues to remain relevant: the family of ‘design arguments’ for the existence of God.
Design arguments are characterized, not surprisingly, by appeals to design. Each such argument urges us to accept that one or another aspect of the world or of things in the world is the product of purposeful, intelligent agency. That is, each design argument attempts to establish that some aspect of the natural world was designed. From there, it is a short mental hop to the existence of a designer. After all, the presence of design in the world surely implies the existence of a designer. For the arguments we will examine, that designer is typically (though not always) understood to be the Christian God.
An Introduction to Design Arguments
- Benjamin C. Jantzen
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The history of design arguments stretches back to before Aquinas, who claimed that things which lack intelligence nevertheless act for an end to achieve the best result. Although science has advanced to discredit this claim, it remains true that many biological systems display remarkable adaptations of means to ends. Versions of design arguments have persisted over the centuries and have culminated in theories that propose an intelligent designer of the universe. This volume is the only comprehensive survey of 2,000 years of debate, drawing on both historical and modern literature to identify, clarify and assess critically the many forms of design argument for the existence of God. It provides a neutral, informative account of the topic from antiquity to Darwin, and includes concise primers on probability and cosmology. It will be of great value to upper-level undergraduates and graduates in philosophy of religion, theology, and philosophy of science.
5 - The golden age of natural theology
- Benjamin C. Jantzen, Virginia College of Technology
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Summary
The rise of natural theology
From among the sparse offerings of the Middle Ages, I presented only the design argument of Thomas Aquinas as worth a close examination. However, there is one more medieval work we ought to consider, if only for its significance as a transitional text. I am referring to a book written in the 1430s by a Spanish professor of medicine, philosophy, and theology named Raymond Sebonde. The importance of this book is not to be found in the specific design argument it contains. In fact, unlike what we saw in the work of Aquinas, it’s no straightforward affair to extract a clear argument from Sebonde. His book was never translated from its original Latin into English (though Montaigne did translate it into French), and those few who have undertaken to study the book in its original form suggest it is almost unreadable. It contains some 330 chapters of poorly rendered and heavily abbreviated Latin. Nonetheless, we can charitably reconstruct the following argument from the third chapter of the text. The “book of nature” is composed of creatures that can be sorted into four “degrees” or “grades” based on their possession or lack of “existence, life, sensation, intelligence, and free will.” In the first grade are things like rocks that have only existence. In the second grade are things like plants that have existence and life, but nothing else. The animals, the third grade of creature, have everything excepting intelligence and free will. Mankind is in a grade of its own, possessing the whole package of characteristics. Now, says Sebonde, the presence of these characteristics must have a cause. The cause cannot be humanity itself – we certainly didn’t give ourselves intelligence or free will – or any of the lower grades of creatures. Thus, the cause must be something with more numerous and more powerful characteristics than humans. Furthermore, the hierarchical order in the grades of creatures – man above animals above plants above minerals – could only result from the intention of an intelligent creator. Lastly, we know there’s only one creator since the characteristics are the same for each grade in which they appear and therefore must have the same cause. That intelligent, powerful cause is God.