 Welcome back to 19th and 20th century philosophy. I'm Matt Brown and I'm here to talk to you today about Gottlob Frege. Frege was a German philosopher, born in 1848, died in 1925. Frege was known as a logician, mathematician, and philosopher. He worked primarily at the University of Jena, which is in modern-day Germany. He's known sometimes as the grandfather of analytic philosophy, and let me just mark a strange little note there. Sometimes the distinction is drawn between analytic philosophy and continental philosophy, and yet Frege is coming from continental Europe, Germany, where many of the other continental philosophers come from. It's kind of strange. So as I said, Frege is known for his work in logic, mathematics, and philosophy. He was particularly interested in formal logic. He created the first modern formal predicate logic, as well as the first fully axiomatic logical system. Within mathematics, he was particularly interested in the foundations of mathematics. So what is the sort of basis of mathematical truth and knowledge? And there, he was a defender of what's called logicism. He attempted to ground the foundations of mathematics in logic, in formal logic. This is something that Bertrand Russell and Alfred North Whitehead would also try to do, a little bit later on. And ultimately, it's a project that's seen as a failure for reasons that came about in the later part of the 20th century with the mathematician Godel, Kurt Godel, and his incompleteness theorems. In both logic and mathematics, Frege was a defender of what's called anti-psychologism. So he was strongly opposed to a philosophical trend of the late 19th century to attempt to provide foundations for things like logic and mathematics in psychology. I think we've talked before about how psychology became a really important part of the philosophical scene in the late 19th century. And by psychology, I mean, of course, empirical or experimental psychology. And there was a reaction against that towards the end of the 19th and the beginning of the 20th century. And Frege was perhaps one of the most important figures in that area. Another very important figure in the anti-psychologism movement, perhaps more well known at the time, was a philosopher by the name of Edmund Husserl, who we'll talk about next. Husserl is the founder of the School of Phenomenology and also considered, therefore, a father or grandfather of continental philosophy. But Husserl, like Frege, was really interested in the early part of his career, particularly in the foundations of mathematics. He wrote early works on the foundations of arithmetic. He was also interested to some extent in logic, one of his major most ambitious works is called the Logical Investigations. And in his most early writings, Husserl is a proponent of psychologism. He's a proponent of the idea that we should found our knowledge of arithmetic and mathematics more generally in psychology. You want to know what a number is, you want to know how we know things about numbers, what the truth about numerical knowledge and arithmetic knowledge is. Early Husserl said, you've got to look to psychology. These are psychological functions. Frege critiqued Husserl, wrote a critique and published it about Husserl's philosophy arithmetic. Frege and Husserl also wrote letters to each other and shared drafts of work with each other. And Frege convinced Husserl that psychologism was untenable. It's a big twit prop airplane up there. Frege convinced Husserl that psychologism was untenable. And so in later work, Husserl also wrote and against psychologism as part of the anti-psychologist movement. So there's a significant influence between Frege and Husserl. And I'll talk about that more in the video on Husserl. The last part of Frege's philosophy that I'll talk about is his philosophy of language. So in trying to suss out formal logic and the nature of logic and trying to ground mathematics in logic, Frege found that in many ways he needed to understand meaning and symbolic language, the nature of language in a more general sense. So this led Frege into investigations of the nature of concepts, the nature of meaning, the nature of the denotation or reference of terms. And that's something that Frege, perhaps even more influential than his work in mathematics today within philosophy, at least, his philosophy of language remains pretty important. So Frege's philosophy of language is motivated by a series of puzzles about the meaning of certain kinds of expressions. For example, Frege noticed that the expression A is A equals A, or the expression, let's say, 12 equals 12, or the expression Clark Kent is Clark Kent. These are all relatively trivial, meaningful, but not very informative statements. They basically tell us that something is the same as itself. On the other hand, there are different kinds of similar statements that seem importantly different. So statements like A equals B, or 3 plus 9 equals 12, or Clark Kent is Superman, that, unlike these statements, seem to be different. They seem to be informative in a way that these statements are not. They seem to carry meaning that are not there in this statement. But that's puzzling for Frege, because if this statement is true, if A equals B is true, then A and B are just different names for the same thing. If 3 plus 9 equals 12 is true, then 3 plus 9 and 12 are just different ways of writing the same number. And if it's true that Clark Kent is Superman, then these are just different names for the same person. These all say that the same thing is identical to itself in just the way that these do. So the fact that these seem to have a different meaning from these was a puzzle for Frege. Similarly, you might imagine a statement like Lois Lane believes that the Clark Kent is clumsy might be true. But Lois Lane believes that Superman is lazy. That seems to be false, right? Given what we know about Lois Lane, before she knows that Clark Kent is Superman, she's going to have different beliefs about him. But how is it that this statement can be true and this statement can be false when a part of the statement, this part here, these denote the same thing. These refer to the same person. So how can the meaning of these two statements differ? This is the puzzle that motivates a significant insight of Frege's philosophy of language. So what did Frege do to address this problem? These are these puzzles, right? On the one hand, you have sentences and expressions in which you have different terms substituted, but the terms refer to the same things. So what Frege did to address this problem is he posited two dimensions to our understanding of meaning. On the one hand, you have reference. The reference of a term or concept is its denotation, the object it refers to, the thing that it denotes, right? So if it's proper name, it's the person that the name names. If it's a concept, it may be the type of thing in the world that it refers to. The other dimension, the second dimension of meaning is what Frege called sense. So the notion of sense has been somewhat more difficult for Frege's interpreters to understand. The basic idea is that the sense of a concept or term is the meaning of that term in the sense of the thought or representation that it expresses, right? So while the denotation of Carol Danvers and Captain Marvel are the same, they refer to the same person or they would in the world where they were Carol Danvers and Captain Marvel exist, their sense of those terms is different to the representation or thought associated with Captain Marvel versus Carol Danvers is very different. Similarly, the morning star and the evening star, even though they're the same star, are the thought that we associate with those terms is different. And that is how the identity statements between two different terms with the same reference or denotation can still be meaningful. And similarly, that's how a statement like Bob is in love with Carol Danvers and Bob is in love with Captain Marvel can have different truth values, right? Because in a context like belief or love or desire, it's the sense, it's the representation or thought associated with that term that matters and not just the reference by itself. Now, all that said, there's a really important caveat to the way I've been describing Frege's concept of sense. And that's, remember, I told you, Frege is an anti-psychologist, right? That is, he is against psychologic understanding or interpretation of these key philosophical concepts. And that goes as much for the theory of meaning in philosophy of language as it does for his logic or foundations of mathematics work. So strictly speaking, the sense of a concept is not a thought in the psychological sense. It is rather the case that for Frege, there is an objective thought associated with every concept. And there is a kind of, if you like, platonic realm of ideas in which every concept gets its objective sense. That at least is one way to interpret what Frege is saying, but it is a little difficult. Naturally, these are the ideas in the essay on sense and reference that we'll be discussing this week. And so there's a lot more to say about these core concepts and what they mean. But that's a sort of introduction into thinking about sense and reference in the context of Frege's life and works. So I look forward to hearing what you think about these ideas and talking with you about them on Discord in class or in the comments of the video. I will see you again soon to talk about Edmund Husserl. Have a good night.