On March 13, 2016, Hilary Whitehall Putnam (1926-2016), professor of philosophy at Harvard University, died at home at the age of 90. Putnam is well-known in European and American academic circles and was once hailed as “the living fossil of American philosophy.” He has drawn a magnificent philosophical map for us with 24 monographs and more than 300 papers. His academic advantages span mathematics, philosophy, psychology, computer science and other disciplines, and he has made outstanding achievements in philosophical branches such as mathematical philosophy, philosophy of mind, and philosophy of language. Putnam changed his academic stance many times and had the courage to revise his views, so much so that some criticized him as a philosopher with “unstable and fickle thinking”. He often warned people that when explaining his thoughts, they must mark the time, because it may not be long before he himself will give up or even deny that idea and put forward new or even completely opposite viewpoints. It is this kind of self-reflection and self-correction that keeps Putnam always at the forefront of academic debates and leading the way.
Many scholars highly recognize and appreciate Putnam’s academic attitude because he represents a spirit of positivity, constant exploration, and innovation. After Putnam’s death in 2016, University of Chicago philosopher Martha Nussbaum compared Putnam to Aristotle and spoke highly of the several ideological changes that Putnam experienced throughout his life. The eulogy for Putnam said: “Most philosophers will argue in the form of arguments, but they will eventually fall into dogma. No matter what new arguments say, most people will go to any lengths to defend clichés. Defense. Putnam’s glory lies precisely in the fact that he never stuck to his own way of thinking about philosophy, because he always followed the arguments and often changed his views. His changes were not due to external pressure, but entirely out of his own interest. This humility makes him fully worthy of the honor of reason.”
Mathematician or philosopher?
Although Putnam’s status in English philosophy is at its peak, he entered the academic arena as a mathematician in his early years. But later, in contrast to his status as a philosopher, his title of mathematician seemed not to be so eye-catching. In any case, in his early years he was more interested in mathematics than philosophy.
Putnam’s mathematical beginnings date back to his teenage years. When he was studying at Central High School in Philadelphia, Pennsylvania, he had two very good friends. One was Norman Tyson Hamilton, who devoted himself to becoming a mathematician out of his love for mathematics; One is William Turanski, who is considered one of the pioneers of modern computer science. The two of them had frequent exchanges with Putnam over the years, discussing certain “bugs” (loopholes) in mathematics, which aroused Putnam’s great interest in mathematics. Since high school, Putnam has always had a passion for solving unknown puzzles.
From 1948 to 1949, Putnam began his graduate studies at Harvard University. He called his year of study at Harvard “my career as a mathematician.” For Putnam, this period was as important as his philosophical career. He once said in his autobiography of the album “The Philosophy of Hilary Putnam” (2015) in the famous “Library of Living Philosophers” series: “Apart from my career as a philosopher, my career as a mathematician is the most satisfying to me.”
In the following years, Putnam overcame many problems in the field of mathematics and published more than 30 academic papers related to mathematics. In 1960, he received tenure in the Department of Mathematics at Princeton University. He also taught professional courses and supervised doctoral dissertations in the Department of Mathematics at MIT and Harvard University.
However, what was the reason that led him to turn to philosophy and devote his life to it? Unlike his early enthusiasm for mathematics, Putnam regarded his youthful interest in philosophy as a very childish manifestation. His philosophical enlightenment can also be traced back to middle school, when he founded a small philosophy club in school. But as a middle school student, Putnam did not connect philosophy with his own career. Instead, he wanted to be an excellent writer like his father, Samuel Putnam, or become like Hausman. A dashing poet like Alfred Housman and Algernon Swinburne, or an accomplished mathematician like his two good friends.
Compared with mathematics, Putnam’s interest in philosophy may have lagged behind. However, what is rare is that he has a solid foundation in philosophy. Not only does he have a real academic background, but his mentors are almost all the top philosophers in the world. .
In 1945, Putnam formally took courses related to philosophy at the University of Pennsylvania. Here he met the teachers who led him to the palace of philosophy, such as C. West Churchman, Sidney Morgenbesser, Richard Rudner, etc., who later became Putnam’s lifelong friends. Academic friends. During his graduate studies at Harvard University, Putnam was taught by the famous logical empiricist Willard Van Orman Quine, and also took philosophy courses with three other outstanding philosophers: Morton White’s American philosophy courses, Clarence Irving Lewis’ theory of knowledge course, and Harry Austryn Wolfson’s Spinoza course. He then went to the West Coast to continue his studies at the University of California, Los Angeles. In 1951, he completed two years of doctoral studies under the guidance of Professor Hans Reichenbach, a philosopher from Germany, and obtained a doctorate in philosophy. Putnam devoted his life to philosophical research and was inseparable from the influence of this former representative of the Berlin School. Putnam later deliberately “imitated” Reichenbach: “Some of my former students often praised me because I like to think and write about ‘big questions’ rather than some technical issues, and these are exactly what Reichenbach taught me. . He often taught me: Being an analytic philosopher does not mean rejecting the ‘big questions’.” Putnam often said that whether it is academic seriousness or optimism in life, Reichenbach is The best teacher he had ever had.
A good teacher is like a beacon, lighting the way forward for Putnam. In 1953, Putnam met Rudolf Carnap, a representative of the Vienna Circle from Austria, at Princeton University. At that time, Carnap was already world-famous, and Putnam was just an ordinary junior teacher. He had just started working and had no research projects or original ideas. However, Carnap never looked down on him, but respected him very much, which moved Putnam quite a lot. When Putnam was confused, Carnap often took the initiative to talk to him. Sometimes he told him about his interesting experiences to relax him; sometimes he shared some philosophical views with him. The two of them would even “quarrel” because of their different opinions, but after the argument, Putnam would always burst out with new ideas. It was Carnap who extended a helping hand when Putnam lacked self-confidence and needed encouragement the most, and led Putnam onto the correct academic path.
Thinking about the Mind—Creating Functionalism
Before Putnam, there were two main mainstream views in the field of philosophy of mind. The first view is behaviorism, that is, our psychological state can be expressed through external behaviors or behavioral tendencies. For example, if you feel hot, we can see the psychological state of “hot” through your constant fanning or the dripping of your sweat. The second view is type identity theory, which believes that we can find corresponding substances for each mental state to associate with it. Each type of mental event is a type of physical event. But Putnam disagreed with either view. In his view, mental state cannot be simply reduced to behavioral state or brain state. He firmly believes that mental state is a functional state, which is inspired by a certain behavior when we have beliefs about the world and have certain desires. Causes are characterized by certain causal connections with external stimuli (input from the senses), behavioral responses, and other mental states such as beliefs and desires. Functional states do not depend on any specific type of matter, but can be realized in a very diverse range of hardware—whether it is a human brain, a computer brain, or aliens with different evolutionary histories and biological makeups.
Functionalism is Putnam’s most important contribution to the philosophy of mind. He adopted the functionalist approach to provide a possible solution to the traditional mind-body problem. In 1954, Carnap invited Putnam to a small meeting. One of the main contents of the meeting was the nature of psychological concepts. This discussion aroused Putnam’s strong interest. But what kind of opportunity led Putnam to explore the philosophy of mind? There seems to be no clear event related to it. He regards the beginning of his journey of spiritual philosophy as a smooth process. In the 1960s, Putnam was already a well-known mathematician, logician and philosopher. At this time, it was an era of rapid development of science and technology. Against this background, he conceived the idea of human “mind”. It’s no surprise that “state” is a computer state.
In 1960, Putnam published the paper “Minds and Machines”, which formally elaborated on this idea that had been conceived in his mind countless times. He believed that the difficulties of traditional mind-body problems were always related to language and logic, and always relied on empirical facts; he tried to show that all problems could be answered through a computational system, and this solution had nothing to do with experience. In 1967, Putnam published two more papers, “The Mental Life of Some Machines” and “The Nature of Mental States”, continuing to defend the functionalist theory. Putnam’s version of the theory can be called “strong artificial intelligence” or “Turing machine functionalism” because he was partly inspired by the British mathematician Alan Turing’s ideas about Turing machines. . Putnam believes that Turing machines have various structures, which can be manual or mechanical, and we should not just regard it as a machine, it is actually an abstract computing tool, mainly Responsible for the input and output of information and the internal state when information is processed. So imagine a machine responsible for operating various biological psychological states – the process may be different in different organisms, but the entire computational work will be completed successfully.
The famous thought experiment—”Twin Earth” and “Brain in a Vat”
Putnam’s most famous contributions to philosophical research are undoubtedly his two famous thought experiments. In 1975, he designed a “Twin Earth” experiment in his paper “The Meaning of “Meaning””. Suppose there is a planet in the solar system that replicates our Earth in every detail. The languages spoken by the people living there and their spiritual activities (such as beliefs) are exactly the same as ours on Earth. Putt Nan calls this replica “Twin Earth.” On Twin Earth, there is something that looks, feels, tastes and even functions exactly like water on Earth. The chemical formula of what we call “water” on Earth is H2O, but the chemical formula of what people on “Twin Earth” call “water” is XYZ. So even though the inhabitants of Twin Earth have the same internal state as we do, when they say the word “water” they are referring to a substance with chemical composition XYZ; and when we say “water” By this term, we are referring to substances whose chemical composition is H2O. —The two words for “water” cannot have the same meaning. Putnam concluded from this that the meaning of words in a language is not just “in the mind” but depends, at least in part, on facts in the external world. This is the theory of “semantic externalism” that he developed based on the “Twin Earth” thought experiment. In light of this, Putnam rejects traditional notions of meaning.
In 1981, Putnam published his seminal work “Reason, Truth and History”, in which he proposed the “Brain in a Vat” experiment in the first chapter of the book. Later, this thought experiment provided people with a lot of material about the virtual world, such as the famous American science fiction novel “Avalanche” and the movies “The Matrix”, “Inception”, “Ready Player One”, etc., all of which continued the “brain in a vat” Thought experiment inspiration. In recent years, with the development of cognitive science and artificial intelligence technology, “brain in a vat” experiments are no longer limited to the creation of science fiction works, but have become a cutting-edge theme in the exploration of artificial intelligence and information technology, such as “brain-computer interface”, VR The emergence of concepts such as , AR, and the metaverse are also related to this.
Have questions like this ever arisen in your mind: Does our world really exist? Are we real individuals in this world? These formulations may seem absurd, but their connotations are worth pondering. Putnam describes a situation in which an evil scientist performs an operation in which he cuts a man’s brain from his body and places it in a vat containing a nutrient solution that keeps the brain alive; The nerve endings of the brain are connected to a supercomputer. The computer completely controls the brain in the tank, making the “master” of the brain completely unaware of the changes in the situation. For him, the people, objects, sky, etc. around him still exist. , just like the real environment. In reality, however, everything the person experienced was the result of a computer delivering electrical impulses to the nerve endings in the brain. The computer’s intelligence is so high that if the person wants to raise his hand, the computer’s feedback will cause him to “see” and “feel” his hand raised. Evil scientists can also change the computer program to make the person “experience” any situation or environment according to the scientist’s will. Then we came up with a more “bold” idea: a supercomputer controls the entire world, creating a “collective hallucination” for the entire human race. So the question then becomes: How do you make sure you’re not the one in this predicament?
However, after putting forward this contemporary skeptical experiment, Putnam immediately refuted it. He believed that “the reason why we can ask the question of ‘brain in a vat’ just shows that we are not a brain in a vat.” . And if we are brains in a vat, we can neither say nor think the proposition ‘we are brains in a vat’.” According to Putnam, the reason why we are confused about the existence of “brain in a vat” is because we hold a “mysterious” theory of reference, that is, we believe that the events in the mind must correspond to what our words refer to. object. There is an inherent, inner, and mysterious connection between the words we refer to and the things they represent. As long as someone says “brain in a vat”, they must be referring to the “brain in a vat” that is currently in our minds. ” and “brain.” Therefore, the “brain in a vat” hypothesis is self-contradictory.
According to the “brain in a vat” experiment, we may be able to illustrate Putnam’s contribution to contemporary analytic philosophy and philosophy of science through another simple thought experiment: If you are a philosophical researcher, please now tell us about Putnam Remove Putnam’s philosophical thoughts from your own brain, and then examine the remaining philosophical map in your brain. The degree of fragmentation can reflect the extent to which you are influenced by Putnam. If you remove the “Twin Earth” and “Brain in a Vat” thought experiments, is the philosophical landscape in your mind incomplete? The influence of Putnam’s philosophy has spread to hundreds of countries, and his students and many interpreters are still like him, continuing to enrich and extend the philosophical map in our brains.
Since the end of the 19th century, among the group of Anglo-Saxon philosophers, there has been Charles Peirce, the father of pragmatism, John Dewey who proposed that “education is life”, and Wittgenstein, the “genius philosopher”. Ludwig Wittgenstein), Quine who made outstanding contributions to the combination of analytic philosophy and pragmatism, and Paul Feyerabend who gave analytic philosophy a blow, and so on. In this palace of philosophy where a hundred flowers bloom, Professor Putnam occupies a place with his unique way of thinking and his achievements in writings. Putnam’s academic scope is extremely wide, from the early philosophy of logic, philosophy of science, philosophy of mathematics, philosophy of language, metaphysics, philosophy of mind, and theory of knowledge to later ethics, political philosophy, economic philosophy, literary philosophy, and Jewish philosophy. Philosophy etc. Not only that, he has made original and lasting contributions in all the fields he has touched. Thought experiments such as “Twin Earth” and “Brain in a Vat” have become important topics for discussing issues such as skepticism, semantic externalism, and realism. key issues that cannot be avoided.
Putnam was lucky. When he was in his 20s, he met Reichenbach and Carnap, two logical positivists from continental Europe, and had in-depth academic exchanges with them. This made him later One of the factors that makes him one of the most famous philosophers in the world. The famous contemporary American philosopher Richard J. Bernstein highly praised Professor Putnam’s influence on philosophy in today’s world: “If we want to write the most important and exciting philosophy in the past half century, history of debate, it is most appropriate to begin with the philosophy of Hilary Putnam.”