A

A difference that does not make a difference is not a difference at all.
-- Anon. Pragmatist's Motto

Put your model where your mouth is.
-- Anon. Philosophical Modeling Credo

B

On two occasions I have been asked [by members of Parliament!], "Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?" I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.
-- Charles Babbage

For ideas, fame is fortune. And nothing makes you famous faster than an audience willing to distribute your work for free.
-- John Perry Barlow, The Next Economy Of Ideas

Cyberspace is unreal estate. Relationships are its geology.
-- John Perry Barlow, The Next Economy Of Ideas

A system is computational just in case adopting the computational stance to that system offers useful generalizations and predictions about the operation of the system, over and above those generated by not adopting such a stance.
-- Istvan Berkeley, Re: Searle's challenge, The Monist Interactive Issue

Nothing is more practical than a good theory.
-- Ludwig Boltzmann 

C

If one is interested in the relations between fields which, according to customary academic divisions, belong to different  departments, then he will not be welcomed as a builder of bridges, as he might have expected, but will rather be regarded by both sides as an outsider and troublesome intruder.
-- Rudolf Carnap, Intellectual autobiography

Algorithmic information theory (AIT) is the result of putting Shannon's information theory and Turing's computability theory into a cocktail shaker and shaking vigorously. The basic idea is to measure the complexity of an object by the size in bits of the smallest program for computing it.
--G. J. Chaitin

...the relation between an implemented computation and an implementing system is one of isomorphism between the formal structure of the former and the causal structure of the latter. In this way, we can see that as far as the theory of implementation is concerned, a computation is simply an abstract specification of causal organization.
-- David Chalmers, A Computational Foundation for the Study of Cognition

Much of theoretical physics has traditionally been concerned with trying to find "shortcuts" to nature. That is to say, with trying to find methods that are able to reproduce a final state of a system by knowing the initial state but without having to meticulously trace out each step from the initial to final states. The fact that we can write down a simple parabola as a path a thrown object makes in a gravitational field is an example of an instance where this might be possible. Clearly such shortcuts ought to be possible in principle if the calculation is more sophisticated than the computations the physical system itself is able to make. But consider a computer. Because a computer is itself physical system, it can determine the outcome of its evolution only by explicitly following it through. No shortcut is possible. Such computational irreducibility occurs whenever a physical system can act as a computer. In such cases, no general predictive ability is possible. Computational irreducibility implies that there is a highest level at which abstract models of physical systems can be made. Above that level, one can model only by explicit simulation.
-- David Chalmers, A Computational Foundation for the Study of Cognition

Computational universality is a property of a certain class of computers such that changes in input alone allow any computable function to be evaluated without any change in internal construction. Universal computers can thus simulate the operation of any other computer, given that their input is suitably coded. Conway's Life Game, for example, has been shown to be a universal computer. This means that with a proper selection of initial conditions (i.e. the initial distribution of "live" and "dead" cells), Life can be turned into a general purpose computer. This fact fundamentally limits the overall predictability of Life's behavior. The Halting Theorem, for example, asserts that there cannot exist a general algorithm for predicting when a computer will halt its execution of a given program. Given that Life is a universal computer -so that the Halting theorem applies -this means that one cannot, in general, predict whether a particular starting configuration of live and dead cells will eventually die out. No shortcuts are possible, even in principle.
-- David Chalmers, A Computational Foundation for the Study of Cognition

The goal of research in evolutionary psychology is to discover and understand the design of the human mind. Evolutionary psychology is an approach to psychology, in which knowledge and principles from evolutionary biology are put to use in research on the structure of the human mind.... In this view, the mind is a set of information-processing machines that were designed by natural selection to solve adaptive problems faced by our hunter-gatherer ancestors.
-- Leda Cosmides & John Tooby, Evolutionary Psychology Primer

Every aspect of an organism's phenotype is the joint product of its genes and its environment. To ask which is more important is like asking, Which is more important in determining the area of a rectangle, the length or the width? Which is more important in causing a car to run, the engine or the gasoline? Genes allow the environment to influence the development of phenotypes.
-- Leda Cosmides & John Tooby, Evolutionary Psychology Primer

...the deep paradox uncovered by AI research: the only way to deal efficiently with very complex problems is to move away from pure logic... Most of the time, reaching the right decision requires little reasoning... Expert systems are, thus, not about reasoning: they are about knowing ... Reasoning takes time, so we try to do it as seldom as possible. Instead we store the results of our reasoning for later reference...
-- Daniel Crevier, "The Tumultuous History of the Search for Artificial Intelligence," 1993.

God is a hacker.
-- Francis Crick

If the automobile had followed the same development cycle as the computer, a Rolls-Royce would today cost $100, get a million miles per gallon, and explode once a year, killing everyone inside.
-- Robert X. Cringely, InfoWorld magazine

D

Just as you cannot do very much carpentry with your bare hands, there is not much thinking you can do with your bare brain.
-- Bo Dahlbom and Lars-Erik Janlert (unpublished)

If you want to understand life, don't think about vibrant, throbbing gels and oozes, think about information technology.
-- Richard Dawkins, The Blind Watchmaker

There is a popular cliche ...which says that you cannot get out of computers any more than you have put in..., that computers can only do exactly what you tell them to, and that therefore computers are never creative. This cliche is true only in a crashingly trivial sense, the same sense in which Shakespeare never wrote anything except what his first schoolteacher taught him to write words.
-- Richard Dawkins, "The Blind Watchmaker"

In a universe of electrons and selfish genes, blind physical forces and genetic replication, some people are going to get hurt, other people are going to get lucky, and you won't find any rhyme or reason in it, nor any justice. The universe that we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil, no good, nothing but pitiless indifference.
-- Richard Dawkins 'God's Utility Function', Scientific American

We are survival machines - robot vehicles blindly programmed to preserve the selfish molecules known as genes. This is a truth which still fills me with astonishment.
-- Richard Dawkins, The Selfish Gene

The river of my title is a river of DNA, and it flows through time, not space. It is a river of information, not a river of bones and tissues; a river of abstract instructions for building bodies, not a river of solid bodies themselves.
-- Richard Dawkins, River Out of Eden

Reductionism is explanation. Everything must be explained reductionistically. But it must be explained hierarchically and in step-by-step reductionism. Greedy reductionism, or precipice reductionism, is a leap from the top of the hierarchy down to the bottom of the hierarchy in one step. That you can't do: you wont explain anything to anybody's satisfaction.
-- Richard Dawkins, in The Third Culture

There's not a thing that's magical about a computer. One of the most brilliant things about a computer is that there's nothing up its sleeve. We know to a moral certainty there are no morphic resonances, psionic waves, spooky interactions; it's good old push-pull, traditional, material causation. And when you put it together by the trillions, with software, with a program, you get all of this magic that's not really magic.
-- Daniel C. Dennett, The Computational Perspective

Almost any process can be interpreted through the lens of computational ideas, and usually - not always - that's a fruitful exercise of reinterpretation. We can see features of the phenomena through that lens that are essentially invisible through any other lens, as far as we know.
-- Daniel C. Dennett, The Computational Perspective

Memes now spread around the world at the speed of light, and replicate at rates that make even fruit flies and yeast cells look glacial in comparison. They leap promiscuously from vehicle to vehicle, and from medium to medium, and are proving to be virtually unquarantinable.
-- Daniel Dennett, Consciousness Explained

The juvenile sea squirt wanders through the sea searching for a suitable rock or hunk of coral to cling to and make its home for life. For this task, it has a rudimentary nervous system. When it finds its spot and takes root, it doesn't need its brain anymore so it eats it! (It's rather like getting tenure.)
-- Daniel Dennett, Consciousness Explained

Connectionist models are ultimately evolutionary. They involve the evolution of connection strengths over time.
-- Daniel C. Dennett, in The Third Culture, p183

If you look at the history of philosophy, you see that all the great and influential stuff has been technically full of holes but utterly memorable and vivid. They are what I call "intuition pumps"-- lovely thought experiments. Like Plato's cave, and Descartes's evil demon, and Hobbes' vision of the state of nature and the social contract, and even Kant's idea of the categorical imperative. I don't know of any philosopher who thinks that any one of those is a logically sound arguement for anything. But they're wonderful imagination grabbers, jungle gyms for the imagination. They structure the way you think about a problem. These are the real legacy of the history of philosophy.
-- Daniel C. Dennett, in The Third Culture

Computer Science is no more about computers than astronomy is about telescopes.
-- E. W. Dijkstra

Teaching to unsuspecting youngsters the effective use of formal methods is one of the joys of life because it so extremely rewarding. Within a few months, they find their way into a new world with a justified degree of confidence that is radically novel for them; within a few months, their concept of intellectual culture has acquired a radically new dimension. To my taste and style, that is what education is about.
-- Edsger W. Dijkstra. "On the Cruelty of Really Teaching Computing Science"

In the beginning there was information. The word came later.
--Fred Dretske, Knowledge and the Flow of Information

Emergent behavior is that which cannot be predicted through analysis at any level simpler than that of the system as a whole... Emergent behavior, by definition, is what's left after everything else has been explained.
-- George B. Dyson, "Darwin Among the Machines: The Evolution of Global Intelligence," p9, 1997.

E

As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality.
-- Albert Einstein

F

There's no such thing as a free lunch.
-- Milton Friedman (attributed), Bartlett's Familiar Quotations

G

Now, most single accidents make very little difference to the future, but others may have widespread ramifications, many diverse consequences all traceable to one chance event that could have turned out differently. Those we call frozen accidents.
-- Murray Gell-Mann, in The Third Culture

What is wrong is that we have invented the technology to eliminate scarcity, but we are deliberately throwing it away to benefit those who profit from scarcity.
-- John Gilmore, What's Wrong With Copy Protection

The most important scientific revolutions all include, as their only common feature, the dethronement of human arrogance from one pedestal after another of previous convictions about our centrality in the cosmos.
-- Stephen Jay Gould

H

Look after the syntax and the semantics will look after itself
--John Haugeland's Functionalist Motto

To me, the most interesting thing in the world is how a lot of simple, dumb things can organize themselves into something much more complicated that has behavior on a higher level.
-- Daniel Hillis, in The Third Culture

The task of a scientist is to find patterns in nature. There is always the danger that one will see patterns were there are none.
--John Horgan, The End of Science

The ends cannot justify the means for the simple and obvious reason that the means employed determine the nature of the ends produced.
--Aldous Huxley, Ends and Means, 1937

The chessboard is the world, the pieces are the phenomena of the universe, the rules of the game are what we call the laws of nature.
-- T.H. Huxley, A Liberal Education, 1868

I

J

...I can't define my wife, but I can recognize her.
--E. Atlee Jackson, as quoted by John Horgan, The End of Science

K

There is nothing more basic to thought and language than our sense of similarity; our sorting of things into kinds.
-- Immanuel Kant

It is easier to make a theory of everything than it is to make a theory of something.
-- Aharon Katchalsky, as quoted by George Oster

I never satisfy myself until I can make a mechanical model of a thing. If I can make a mechanical model I can understand it. As long as I cannot make a mechanical model all the way through I cannot understand ... 
--- Lord Kelvin 

The process of preparing programs for a digital computer is especially attractive, not only because it can be economically and scientifically rewarding, but also because it can be an aesthetic experience much like composing poetry or music.
-- Donald E. Knuth

The human brain has about 100 billion neurons. With an estimated average of one thousand connections between each neuron and its neighbors, we have about 100 trillion connections, each capable of a simultaneous calculation... (but) only 200 calculations per second... With 100 trillion connections, each computing at 200 calculations per second, we get 20 million billion calculations per second. This is a conservatively high estimate... by the year 2020, (a massively parallel neural net computer) will have doubled about 23 times (from 1997's $2,000 modestly parallel computer that could perform around 2 billion connection calculations per second) ... resulting in a speed of about 20 million billion neural connection calculations per second, which is equal to the human brain.
-- Ray Kurzweil, "The Age of Spiritual Machines", 1999

L

Nature has learned how to bring about organization without employing a central organizer, and the resulting organizations seem much more robust, adaptive, flexible, and innovative than those we build ourselves that rely on a central controller.
-- Christopher G. Langton, in The Third Culture

From an engineering perspective, there are two ways to make something bigger: One is to make it physically bigger, (and human beings spent a lot of time making things physically bigger, working out ways to deliver more power to systems, working out ways to actually build bigger buildings, working out ways to expand territory, working out ways to invade other cultures and take over their territory, etc.) But there's another way to make things bigger, and that's to make things smaller. Because the real size of a system is not how big it actually is, the real size is the ratio between the biggest part of a system and the smallest part of a system. Or really the smallest part of a system that you can actually put to use in doing things.
-- Seth Lloyd, Moore's Law and the Ultimate Laptop

Every physical system, just by existing, can register information. And every physical system, just by evolving according to its own peculiar dynamics, can process that information. I'm interested in how the world registers information and how it processes it. Of course, one way of thinking about all of life and civilization is as being about how the world registers and processes information.
-- Seth Lloyd, Moore's Law and the Ultimate Laptop

Everything that's worth understanding about a complex system, can be understood in terms of how it processes information.
-- "Lloyd's Hypothesis", named after Seth Lloyd, Moore's Law and the Ultimate Laptop

... adaptation has been achieved by the process, already mentioned, which hinges on the gaining of information by means of genetic change and natural selection, as well as on the storing of knowledge in the code of the chain molecules in the genome. 
-- Konrad Lorenz, Nobel Prize lecture, 1973 

M

The brain's functions simply aren't based on any small set of principles. Instead they're based on hundreds or perhaps thousands of them. In other words, I'm saying that each part of the brain is what engineers call a kludge-- that is, a jury-rigged solution to a problem, accomplished by adding bits of machinery wherever needed, without any general, overall plan: the result is that the human mind-- which is what the brain does-- should be regarded as a collection of kludges.
-- Marvin Minsky, from in The Third Culture

It may well be that the way to build an intelligence is just to get your hands on dirty engineering problems. We don't have a theory of automobiles. We have good cars, but there are no fundamental equations of automotive science.
-- Hans Moravec. Quoted by Daniel Crevier, "The Tumultuous History of the Search for Artificial Intelligence," 1993

N

The deadly paradox of the information society is this: The more others know about us, the better they can serve us and deliver the services we require. But the more they know, the more likely are the misuses and the selling of private data, threatening privacy.
-- Donald A. Norman, informationweek.com, Jan. 3, 2000

O

P

A good adaptationist explanation needs the fulcrum of engineering analysis that is independent of the part of the mind we are trying to explain. The analysis begins with a goal to be attained and a world of causes and effects in which to attain it, and goes on to specify what kinds of designs are better suited to attain it than others.
-- Steven Pinker, How the Mind Works

Plato said that we are trapped inside a cave and know the world only through the shadows it casts on the wall. The scull is our cave, and mental representations are the shadows. The information in an internal representation is all that we can know about the world. Consider, as an analogy, how external representations work. My bank statement lists each deposit as a single sum. If I deposited several checks and some cash, I cannot verify whether a particular check was among them; that information was obliterated in the representation. What's more, the form of the representation determines what can easily be inferred from it, because the symbols and their arrangement are the only things a homunculus stupid enough to be replaced by a machine can respond to. Our representation of numbers is valuable because addition can be performed on the numbers with a few dronelike operations: looking up entries in the addition table and carrying digits. Roman numerals have not survived, except as labels or decorations, because addition operations are far more complicated with them, and multiplication and division operations are practically impossible.
-- Steven Pinker, How the Mind Works

Information is nothing special; it is found wherever causes leave effects. What is special is information processing. We can regard a piece of matter that carries information about some state of affairs as a symbol; it can "stand for" that state of affairs. But as a piece of matter, it can do other things as well-- physical things, whatever that kind of matter in that kind of state can do according to the laws of physics and chemistry.
-- Steven Pinker, How the Mind Works

Our goals are the subgoals of the ultimate goal of the genes, replicating themselves.
-- Steven Pinker, How the Mind Works

Intelligence, then, is the ability to attain goals in the face of obstacles by means of decisions based on rational (truth 
obeying) rules. The computer scientists Allen Newell and Herbert Simon fleshed this idea out further by noting that intelligence consists of specifying a goal, assessing the current situation to see how it differs from the goal, and applying a set of operations that reduce difference.
-- Steven Pinker, How the Mind Works

Information and computation reside in patterns of data and in relations of logic that are independent of the physical medium that carries them.
-- Steven Pinker, How the Mind Works

Information is a correlation between two things that is produced by a lawful process(as opposed to coming about by sheer chance).
-- Steven Pinker, How the Mind Works

Who decides that this mark in this system corresponds to that bit of the world? In the case of the computer, the answer is obvious: we get to decide what the symbols mean, because we built the machine. But who means the meaning allegedly inside us? Philosophers call this the problem of "intentionality"(confusingly, because it has nothing to do with intentions). There are two common answers. One[the causal theory] is that a symbol is connected to its referent in the world by our sense organs. Your mother's face reflects light, which stimulates your eye, which triggers a cascade of templates or similar circuits, which inscribe the symbol mother in your mind. The other[the inferential role theory] answer is that the unique pattern of symbol manipulations triggered by the first symbol mirrors the unique patterns of relationships between the referent of the first symbol and the referents of the triggered symbols. Once we agree, for whatever reason, to say that mother means mother, uncle means uncle, and so on, the new interlocking kinship statements generated by the demons turn out to be uncannily true, time and again.
-- Steven Pinker, How the Mind Works

For many physicists and mathematicians, natural selection seems a repugnant kind of explanation, because it is too kludgey. Its random stochastic variation, and selection by utility seems like an ugly way to arrive at something beautiful, and for a physicist or a mathematician, or someone like Noam Chomsky, whose work has often been mathematical, the favored kind of theory is one where a conclusion can be deduced from a bunch of premises in an elegant deductive system. By the aesthetic of a grammarian, or the aesthetic of a physicist, natural selection seems too ugly and weak.
-- Steven Pinker, in The Third Culture

Q

To be is to be the value of a variable.
-- W.V.O. Quine, From A Logical Point of View

Logic chases truth up the tree of grammar
-- W.V.O. Quine, Philosophy of Logic

R

Peter Landin remarked long ago that the goal of his research was "to tell beautiful stories about computation."
-- John Reynolds, Theories of Programming Languages (p. ix)

The supreme maxim of scientific philosophizing: Wherever possible, logical constructions are to be substituted for inferred entities.
-- Bertrand Russell

S

Digital files cannot be made uncopyable, any more than water can be made not wet.
-- Bruce Schneier, The Futility of Digital Copy Prevention

The reason that no computer program can ever be a mind is simply that a computer program is only syntactical, and minds are more than syntactical. Minds are semantical, in the sense that they have more than a formal structure, they have a content.
-- John Searle, Minds, Brains and Science

The 'dirty secret of contemporary neuroscience': we have no idea what the correct level of analysis is, because there is no universally accepted theory of how the brain codes information.
-- John Searle, The Mystery of Consciousness

Learning is any change in a system that produces a more or less permanent change in its capacity for adapting to its 
environment.
-- Herbert A. Simon, The Sciences of the Artificial, The MIT Press, 1996

Representations are themselves objects in the world, and therefore potential objects of (second-order or meta-) 
representations. However, humans seem to be nearly unique in their ability to represent representations.
-- Dan Sperber, 1996, in setting the topic for a conference at Simon Fraser University Feb 7-8, 1997

If poets are the unacknowledged legislators of the world, science-fiction writers are its court jesters. We are Wise Fools who can leap, caper, utter prophecies, and scratch ourselves in public. We can play with Big Ideas because the garish motley of our pulp origins makes us seem harmless.
-- Bruce Sterling in the Preface to Burning Chrome by William Gibson

Formal systems and digital computers are isomorphic. A computer is an instantiation of a formal system, and a formal system is an idealization of a computer.
-- Peter Suber, Formal Systems and Machines: An Isomorphism

If computers can think, then their machine-states can be isomorphic in relevant ways with brain-states. If so, then these machine- and brain-states will be isomorphic in relevant ways with theorems in some formal system. In this sense "artificial intelligence" is a logical problem, even if "intelligence" is not logical. If the "mind" is reducible to the brain and its states, then our mental life is the output of hardware running software, or equivalently, the instantiation of a formal system. Which formal system?
--Peter Suber, Formal Systems and Machines: An Isomorphism

It is better to not be on the web than to be on and not know why.
-- John Sumser

T

One man's modus ponens is another man's modus tollens.
-- Neil Tennant, Philosophia Mathematica, February 1998

There is a remarkably close parallel between the problems of the physicist and those of the cryptographer. The system on which a message is enciphered corresponds to the laws of the universe, the intercepted messages to the evidence available, the keys for a day or a message to important constants which have to be determined. The correspondence is very close, but the subject matter of cryptography is very easily dealt with by discrete machinery, physics not so easily.
-- Alan Turing, as quoted in Cryptonomicon by Neal Stephenson, Avon Books 1999

U

V

W

The gene is a package of information, not an object. The pattern of base pairs in a DNA molecule specifies the gene. But the DNA molecule is the medium, not the message. Maintaining this distinction between the medium and the message is absolutely indispensable to the clarity of thought about evolution.
-- George C. Williams, in The Third Culture

You can speak of galaxies and particles of dust in the same terms, because they both have mass and charge and length and width. You can't do that with information and matter. Information doesn't have mass or charge or length in millimeters. Likewise, matter doesn't have bytes. You can't measure gold in so many bytes. It doesn't have redundancy, or fidelity, or any of the other descriptors we apply to information. This dearth of shared descriptors makes matter and information two separate domains of existence, which have to be discussed separately, in their own terms.
-- George C. Williams, in The Third Culture

Memes, unlike genes, don't have a single, archival kind of medium. Consider the book Don Quixote: a stack of paper with ink marks on the pages, but you could put it on a CD or a tape and turn it into sound waves for blind people. No matter what medium it's in, it's always the same book, the same information.
-- George C. Williams, in The Third Culture

Natural selection, in short, does not anticipate future needs.
-- Edward O. Wilson, Consilience

The love of complexity without reductionism makes art; the love of complexity with reductionism makes science.
-- Edward O. Wilson, Consilience

X

Y

Z