Peter Medawar’s “The Limits of Science”

Owen Hannaway
Owen Hannaway

W.J. Astore

Note to reader: I wrote this back in 1988 when I was a first-year graduate student in the history of science at Johns Hopkins University.  I took my first graduate seminar with Owen Hannaway, a distinguished professor of early modern science and alchemy.  He asked us to do a book review, and I chose Peter Medawar’s The Limits of Science.  I dedicate this article to the memory of Owen Hannaway (1939-2006), a distinguished scholar and a gallant man.

The Limits of Science is an intentionally short book dealing with topics in the history and philosophy of science. It consists of three different essays written in three different styles, yet it yields a general outlook on science which can be nicely summarized.  Sir Peter sees science as the most successful of man’s enterprises, but he is quick to observe that science has limits, although the growth of science itself is not self-limited.

Medawar first defines science.  Science, he says, is not a mere collection of facts but organized knowledge, knowledge that can be used to predict the behavior of the sensible world.  Medawar is careful to emphasize the difficulty of obtaining scientific knowledge, and the need for confidence based on trust within the scientific community.

Medawar then discusses whether there is such a thing as the scientific method and traces the development of different approaches.  Before the Renaissance, deduction in the form of the Aristotelian syllogism was used to advance science, while intuition and revelation were used to support science.  For philosophers in the Middle Ages, divine revelation guaranteed absolute certainty.  Francis Bacon lit a new path for enlightenment in the late sixteenth and early seventeenth centuries through the use of induction.  Bacon’s new method was the development of general premises through the use of experimentation and the collection of observations.  The frontispiece of Bacon’s Novum Organum summed up the new ideal of Plus Ultra (more beyond): it depicted the pillars of Hercules with a biblical inscription (Daniel 12:4) prophesying the advancement of knowledge.

Medawar next examines deduction and induction and finds them lacking.  The chief difficulty with deduction is that it begs the question; it can only discover something already contained in the major premise, therefore it is not a way to new knowledge.  By comparison, a major premise arrived at through induction cannot contain more information than the sum of its known instances.  A theory consisting of a legion of facts summarized by an iterative inductive process can thus be overthrown by a solitary contradictory instance.  In sum, a deductive premise merely makes explicit information that is already present in the premise, while an inductive premise is no better than the sum of its parts.  Neither method leads to new knowledge.

Considering these arguments, Medawar sides with the conclusion of Bertrand Russell and Karl Popper that there is no scientific method.  The myth of induction as the method for scientific advancement, developed by John Stuart Mill and Karl Pearson in the nineteenth century, persists today mainly because it agrees best with the public’s conception of science and the scientist’s desire for a positive self-image.

What then is the catalyst for advances in science? Medawar adopts Shelley’s idea of poesis in poetry: creation through the act of imagination.  The source of scientific hypotheses is these flashes of vision, and it is these hypotheses which guide and limit further science.  Medawar clearly rejects the idea that scientific discovery can be premeditated and cites the role of luck in scientific discovery.  He carefully qualifies the role of luck by showing how the scientist places himself in a certain mindset amenable to luck through his studies and associations with other scientists.

Medawar’s last essay discusses the limits of science. His fundamental assertion is that science does not yield absolute knowledge, and he quotes Kant as support: “Hypotheses always remain hypotheses, i.e., suppositions to the complete certainty of which we can never attain.” Science’s goal then is not the absolute but the nearest approximation possible; the nearer the approximation, the better its predictive capability.

Continuing the discussion, Medawar observes that there could be either a cognitive inadequacy or a restriction arising out of the nature of the human reasoning process that limits the growth of science, but since any such limitations would be present from conception we would never know of them (just as we could never perceive the Pythagorean celestial music due to its continuous presence in our lives). Are there then limits of science?  Not if science is understood as the art of the soluble.  If something is possible in principle, Medawar states, it can be done if the intention is sufficiently resolute and sustained.

The one limit to science as Medawar sees it is that it cannot answer ultimate questions, e.g. “Does God exist?” Medawar goes on to say he is not indicting science; rather he is recognizing that these questions require transcendent answers, which neither arise from nor require validation by empirical evidence.  He actually takes this argument one step further and asserts these questions have no possible answers. (Medawar recognizes that Immanuel Kant felt the opposite; since somehow man’s nature drives him to ask these questions, Kant felt that answers necessarily exist.)

According to Medawar, the question of whether God exists is outside the realm of science; the leap of faith required for a belief in God is one he himself is unwilling to make.  Although Medawar did not personally believe in transcendent answers, he did feel that these answers had a usefulness measured by the peace of mind they bring people.

I bought this book because as a Roman Catholic I was interested in what a scientist had to say about the limits of science in answering ultimate questions.  Medawar confirmed my suspicions that science can play at best only a subsidiary role with regards to these ultimate questions and the religious beliefs they help spawn.

For anyone looking for an introduction into what science is, how it advances, and what questions it can and cannot answer, Medawar’s book is excellent.  Perhaps the one idea I am always left with after reading this book is although science has limits, as long as man retains his ability to create imaginative hypotheses and his inclination to ascertain whether his guesses correspond to reality, there will always be more beyond for intrepid explorers in the realm of science.

Professor Hannaway appended the following note at the end of my review:

“What do you think your reaction would have been if you had read a book by a scientist less sympathetic to the claims of religion?  Perhaps you can find one, read it, and then critically assess the arguments of Medawar.”

“Why do you think a famous scientist like Medawar was so concerned by such questions to write about them in this way?  Could you find out something about his life that might explain this?  Try sources like the Times obituary columns, Nature, Notes and Records of the Royal Society.”

That was Owen: always generous with advice, and always trying to spur you to dig deeper, to learn more.

Bonus Anecdote: I’ll never forget this saying of Owen’s: “Scotch is for after dinner.” The last time I saw him in Denver at a conference, I was really pleased to track down a glass of single malt whisky for him.  He was a wonderful man.

6 thoughts on “Peter Medawar’s “The Limits of Science”

  1. I have been passionately interested in Science since I learned to read and consider myself solidly grounded in the scientific method of thinking/analyzing phenomena. That is, skepticism is essential, results of experiments must be repeatable/verifiable by others, “Extraordinary claims require extraordinary proof” (in the words of Carl Sagan), etc. However, I fully agree that the Ultimate Questions are unanswerable. My mind totally refuses to conceive of all the matter we now can detect in the known Universe (and that yet to be detected!) once concentrated in a sphere the diameter of the period at the end of this sentence (the Big Bang Theory). So, has the Universe always existed? But how can that be? And what, if anything, is “outside” the known Universe? I’m not that interested in this notion of multiple, occasionally intersecting universes–how the hell is any of THAT going to be “proved”? So on the Big Questions I find I am forced to declare: whatever is the correct explanation for how this all came to be, it is indistinguishable from “Magic”!! And so, there is wonder in all of “creation” (careful! tricky word!) and the natural world really needs a lot more respect than humankind is giving it these days. I will conclude with a quote from Vincent Price’s character in the original version of “The Fly,” the brother of the deceased scientist whose work went awry: “The search for truth is the most important job in the world…and the most dangerous.”

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  2. A questioning perspective. I wonder why a “scientist” brings “God” into a philosophical examination of science. To me that is about as related to the topic as asking if science can determine if Santa Claus really existed. (it’s that season)
    Any reading of the history of “God” (or Gods ) based religions only leads me to the question of why does this concept ,inherited from primitive humans all over the world, still persist?
    Today science has determined that the universe is possibly over 10 billion years old and is continuing to expand,. That raises several questions: how small was it in the beginning and what is the media of expansion? The Christians in our country who believe fervently in “God”. also believe that the universe started only 6000 years ago but will also use the fact that science hasn’t answered the questions above as proof that God started the universe.
    I guess it comes down to the fact that I believe more in the scientific “method”,( hard work on hypothesis in the lab or field) as being more important than “luck” coming from “the scientists studies and associations with other scientists”.
    I could continue this but will desist with just the comment that interesting individuals started religions based on gods but soon ambitious power seekers in primitive societies saw that religion as a sure way of gaining and holding political power. And that is where we are today.

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    1. There are so many ways to look at religion. As a Christian, I tend to see Christ as a Platonic idea/ideal: As both God and man, untainted by sin, He was/is the perfect man, the one to whom we should look for guidance. That said, Christ’s teachings are very demanding. Leave behind everything, even your family, to follow Him? Sacrifice all riches? (The latter must create cognitive dissonance in those who embrace the “prosperity Gospel.”) The basic message of most religions, to include Christianity, is love of neighbor, to include attributes like compassion, generosity, charity, and the like. What’s incredible is how often we as humans disobey this basic message, how often we reject it, how often we embrace sin, for want of a better word.

      You can’t “prove” faith. But I can see the evidence of someone’s purity of faith by their actions. Are they compassionate? Are they generous? Are they peace-loving? Do they display humility?

      There is much beauty and wisdom in religion, just as there is in science. Perhaps it is this beauty, this truth, untied to doctrine and dogma, that most speaks to me. Sometimes I feel it in nature or in reading a particularly moving Biblical passage. It “feels” right to me. It speaks to my conscience; my soul, if you will. In those (rare) moments, perhaps there’s some measure of divinity there. I’d like to think so, no matter how subjective or metaphysical it sounds.

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  3. After a long day and a delightful “picker upper”. …..Why does a Jesus need a god? There are many good men and women today who sacrifice like the mythical Jesus and spend their lives in Gulags, Guantanamos, or prisons throughout the world. In this country there are Catholic nuns and priests, atheists, and a scattering of Jews and sundry Protestants also suffering the boot of the state for their work for peace and justice, the same as Jesus did. Where does god fit in? People find spiritual peace in many ways. Jack London’s family came to California as “spiritualists” which was sweeping the country at that time. Did they seek god? When carried too far, seeking God, in my opinion, is antithetical to rational thought and science. I find it hard to trust ‘faith’ when the very tectonic plate the scientists found we live on is slipping and sliding under our feet and who knows where and when, and who knows when a “black hole” in our universe could swallow our little planetary system. And that isn’t even close to what the dysfunction of our political system is doing to me. “Oh ye of little faith’.( or too much?)

    PS I feel a little ‘sin’ occasionally is good for the soul. What I can’t abide is “selfishness” and its subset, “indifference” to the suffering of others.

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    1. Sin is good for the soul? You obviously didn’t go to Catholic school, which is built on guilt. Confess! Repent! I just hope Sister Emily and Sister Jane Elizabeth can forgive you, b. traven.

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  4. I repent! I repent! But can god help this poor sinner stay away from sin.? He’s tried but fails all the time. I’m a dedicated contrarian always looking under rugs, going up blind alleys and god keeps pushing me unto the straight and narrow. But I appreciate your concern about my soul. May peace be with you.

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