Frederick Irwin "Fred" Dretske (; December 9, 1932 – July 24, 2013) was an American philosopher noted for his contributions to epistemology and the philosophy of mind.
Born to Frederick and Hattie Dretske, Dretske first planned to be an engineer, attending Purdue University. He changed his mind after taking the university's only philosophy course, deciding philosophy was the only thing he wanted to do in his life.
After graduating in 1954 with a degree in electrical engineering and serving in the army, he enrolled in graduate school in philosophy at the University of Minnesota, where he received his PhD in 1960. His dissertation, supervised by May Brodbeck, was on the philosophy of time.
Dretske's first academic appointment was to the University of Wisconsin–Madison in 1960, where he rose to the rank of full Professor. In 1988 he was recruited to Stanford University, where he was the Bella and Eloise Mabury Knapp Professor of Philosophy. He remained at Stanford until his retirement in 1998, after which he was professor emeritus in philosophy at Stanford and senior research scholar in philosophy at Duke University until his death.
He was awarded the Jean Nicod Prize in 1994. He was elected a Fellow of the American Academy of Arts & Sciences in 2003.
Upon his death, he was survived by his second wife Judith Fortson, by his children Kathleen Dretske and Ray Dretske, and by a stepson, Ryan Fortson.
Dretske held externalist views about the mind, and thus he tried in various writings to show that by means of mere introspection one actually learns about their own mind less than might be expected. His later work centered on conscious experience and self-knowledge,
Dretske's first book, Seeing and Knowing, deals with the question of what is required to know that something is the case on the basis of what is seen. According to the theory presented in Seeing and Knowing, for a subject S to be able to see that an object b has property P is:
(iii) for the conditions under which S sees b to be such that b would not look the way it now looks to S unless it were P
and (iv) for S, believing that conditions are as described in (iii), to take b to be P.
For instance, for me to see that the soup is boiling – to know, by seeing, that it is boiling – is for the soup to be boiling, for me to see the soup, for the conditions under which I see the soup to be such that it would not look the way it does were it not boiling, and for me to believe that the soup is boiling on that basis.
Knowledge and the Flow of Information (1981)
Dretske's next book returned to the topic of knowledge gained via perception but substantially changes the theory. Dretske had become convinced that information theory was required to make sense of knowledge (and also belief). He signaled this change at the beginning of the new book, opening the Preface with the lines "In the beginning there was information. The word came later." Information, understood in Dretske's sense, is something that exists as an objective and mind-independent feature of the natural world and can be quantified. Dretske offers the following theory of information:
A signal r carries the information that s is F = The conditional probability of s's being F, given r (and k), is 1 (but, given k alone, less than 1).
Thus, for a red light (r) to carry the information that a goal (s) has been scored (is F) is for the probability that a goal has been scored, given that the light is red (and given my background knowledge of the world, k), to be 1 (but less than 1 given just my background knowledge).
With this theory of information, Dretske then argued that for a knower, K, to know that s is F = K's belief that s is F is caused (or causally sustained) by the information that s is F.
His theory of knowledge thus replaced conscious appearances with the idea that the visual state of the observer carries information, thereby minimizing appeal to the mysteries of consciousness in explaining knowledge.
Dretske's work on belief begins in the last third of Knowledge and the Flow of Information, but the theory changed again in the book that followed, Explaining Behavior (1988). There Dretske claims that actions are the causing of movements by mental states, rather than the movements themselves. Action is thus a partly mental process itself, not a mere product of a mental process. For the meaning – the content – of a belief to explain an action, on this view, is for the content of the belief to explain why it is that the mental state is part of a process that leads to the movement it does.