This book was written with me in mind, I am its target reader, so I was delighted when I was invited to read a complimentary copy in exchange for an honest review. As it turns out, the book is easier to read than to review. I decided to judge the book by its cover, and evaluate its claim to be simple, which is not at all the same as being brief or succinct.
The book covers Gödel’s entire life story in such a brief way as to be perfunctory. It gives enough to leave readers curious but dissatisfied, though at the end it recommends further reading which certainly does appeal to me, but it only achieves a limited amount of human interest for this reader. There has to be an implication that, like mathematics, this is not what the reader is looking for here. Simplifying a biography too much does not make it more engaging.
The book omits all mathematics, which makes it accessible to general readers. This can be justified because a general reader, while interested to know that Gödel was a mathematician of the highest stature, is never going to travel further into that maze. It does , though, provide a tourist’s guide to some of Gödel’s work, which covered an impressive range of topics, and it includes a lot of quite entertaining material, notably his speculations on the nature of time.
Having resolved to omit all formal mathematics, the author does decide to present a few simple examples of some standard formulas and arguments in what is called “predicate logic” or “quantificational logic.” This is the logic for which Gödel proved his completeness theorem. [p30] Here we see the term “simple” used in a relativistic sense. It is simple in the sense of being very basic but it is not simple material for the general reader, encountering a language of symbols for the first time. However, it is tolerable and it does end and I found I could proceed without any need to refer back to this section. I am not convinced that it was necessary at all.
Let’s get to the point then. The core of the book just accepts that its target reader really wants to read about Gödel in order to understand better his Incompleteness Theorems and their place in philosophy. This material is not simple, I don’t know why it ought to be or ever could be simple and it would be patronising as well as futile to pass it off as such. Instead of being simple, the explanation is patient, well structured and clearly expressed in plain language. However, the concepts are slippery and I found it necessary to review my highlights several times and to read the full text a number of times before I felt confident that I had a clear impression of what is being said.
So the real benefit of the book’s brevity is that it leaves more time for second and third readings. It would be a shame to enjoy a quick and unruffled reading without taking the time to reflect on its content. That said, the aim of simplicity might actually have been better served by being a bit (even a lot) less succinct at times. Let’s face it: Gödel’s Incompleteness Theorems stopped philosophy in its tracks – it had an immense impact. This introduction for general readers may be set out in simple terms but it is worth taking the time out to work through all the arguments and appreciate their significance. The good thing, based on my own notes and highlights, is that there is more than enough material here to get a decent grounding and the explanations are clear and helpful.
Some quotes to get a flavour:
The axiomatic method has been with us for a long time. More than 2,000 years ago, Euclid applied it to the geometry of his day. Since then, axiomatization has been viewed as an ideal way to systematically organize and unify mathematics and logic.[p28] ... From the small kernel of truths about the domain that the axioms express, the idea is to derive, using valid principles of reasoning, the domain’s other truths...[p29] ... The notion of an axiomatic formal system can thus be made so exact that generating theorems from axioms, based on the rules of inference, is purely mechanical or algorithmic. [p41]
...It is often said that the first incompleteness theorem tells us that mathematical truth is not equal to formal proof. Formal proof is arithmetic in nature, but truth is not. It is also worth keeping in mind that axiomatic formal systems are Turing machines, so we are speaking of the limitations on computers that can do some arithmetic. Such computers cannot be both consistent and complete... As a Platonic rationalist might put it, we uncover more and more arithmetic truths. These truths transcend the axiomatic formal system at each stage. The Platonist would hold that truth is independent of the finite, concrete axiomatic systems or machines and that more truths are, as it were, waiting to be discovered. We can keep ascending on the basis of reason to more truths, but we will always fall short of grasping them all. [p58]
The realm of mathematical truth cannot be regimented into systematic order, as originally intended, by setting out a single fixed set of axioms and rules of inference. We can formally deduce an endless number of truths from any given set of mathematical axioms and rules of inference that are independent of those axioms and rules if the system is consistent. Hence, the theorems come as a blow to anyone who thought the essence of mathematics was, in the end, axiomatic formal reasoning.[p71]
...formal or computational exactness does not always yield certainty. To think otherwise is an illusion. The alleged clarity associated with formal systems is always clarity relative to some background against which the formal system is interpreted. It cannot be strict formalism—blind computation—all the way down. What could clarity amount to without meaning? [p79]
The incompleteness theorems are rigorously proved mathematical theorems about the scope and limits of precisely defined axiomatic formal systems, or Turing machines, in which one can do some arithmetic... Thus, they do not apply to many kinds of texts, such as religious texts—the Bible, Koran, Vedas, Buddhist sutras—and typically not even to theories in the natural sciences. The incompleteness theorems do not show that there are non-material souls, or that some kind of mystical intuition must replace cogent proof in mathematics. They do not provide grounds for despair or mystery-mongering. They do not show that the world in general, or the world of mathematics and logic in particular, is chaotic. They do not imply that truth is relative or accidental. They do not imply that there are only many different interpretations of things and no truth or objectivity. It is correct to say that formal proof is always relative to the axiomatic formal system in which it is defined but the incompleteness theorems drive a wedge between formal provability and mathematical truth. The theorems do not imply that there are absolutely unsolvable mathematical problems. [p82]
Proofs in mathematics have been around for millennia, while strict formalism about proof has existed for only about a hundred years. The theorems do not imply any kind of anti-rationalism or irrationalism. [p83]