Philosophy 024: Big Ideas Prof. Robert DiSalle ( rdisalle@uwo ) Talbot College 408, 519-661-2111 x85763 Office Hours: Mo

1. Philosophy 024: Big Ideas Prof. Robert DiSalle (rdisalle@uwo.ca) Talbot College 408, 519-661-2111 x85763 Office Hours: Monday and Wednesday 11:30-12:30 Course Website: http://instruct.uwo.ca/philosophy/024/

2. Philosophical questions about the computer: What is “intelligence”? What is “thought”? Are these functions that a machine can have? If machines can display “thought” or “intelligence,” does this imply that human cognition is a kind of computational ability? If human cognition is computation, does that imply that the human mind in general is a kind of machine?

3. Some philosophical background to the computer René Descartes, 1596-1650: “Mathesis universalis” G.W. Leibniz (1646-1716): “Universal characteristic,” calculating machine Charles Babbage (1791-1871): Calculating machines George Boole (1815-1864): “The Laws of Thought” Gottlob Frege (1848-1925): “Conceptual Notation” Kurt Gödel (1906-1978): “Formally Undecidable Propositions” Alan Turing (1912-1954): The “Turing Machine”

4. Descartes on how to tell the difference between a human being and a mechanical imitation: “They could never use speech or other signs as we do when placing our thoughts on record for the benefit of others. For we can easily understand a machine’s being constituted so that it can utter words, and even emit some responses to actions on it of a corporeal kind, which brings about a change in its organs…But it never happens that it arranges its speech in various ways, in order to reply appropriately to everything that may be said in its presence, as even the lowest type of man can do…”

5. Descartes: “And the second difference is, that although machines can perform certain things as well as or perhaps better than any of us can do, they infallibly fall short in others, by the which means we may discover that they did not act from knowledge, but only from the disposition of their organs. For while reason is a universal instrument which can serve for all contingencies, these organs have need of some special adaptation for every particular action. …It is morally impossible that there should be sufficient diversity in any machine to allow it to act in all the events of life in the same way as our reason causes us to act.”

6. 1956: Howard Aiken, Harvard University, on the idea of a “universal machine” : “If it should turn out that the basic logics of a machine designed for the numerical solution of differential equations coincide with the logics of a machine intended to make bills for a department store, I would regard this as the most amazing coincidence that I have ever encountered.”

7. Leibniz “When, several years ago, I saw for the first time an instrument which, when carried, automatically records the number of steps taken by a pedestrian, it occurred to me at once that the entire arithmetic could be subjected to a similar kind of machinery so that not only counting, but also addition and subtraction, multiplication and division could be accomplished by, a suitably arranged machine easily, promptly, and with sure results.”

8. Leibniz on the “Universal Characteristic: Although many persons of great ability, especially in our century, may have claimed to offer us demonstrations in questions of physics, metaphysics, ethics, and even in politics, jurisprudence, and medicine, nevertheless they have either been mistaken (because every step is on slippery ground and it is difficult not to fall unless guided by some tangible directions), or even when they succeed, they have been unable to convince everyone with their reasoning (because there has not yet been a way to examine arguments by means of some easy tests available to everyone).

9. Whence it is manifest that if we could find characters or signs appropriate for expressing all our thoughts as definitely and as exactly as arithmetic expresses numbers or geometric analysis expresses lines, we could in all subjects in so far as they are amenable to reasoning accomplish what is done in Arithmetic and Geometry. For all inquiries which depend on reasoning would be performed by the transposition of characters and by a kind of calculus, which would immediately facilitate the discovery of beautiful results. For we should not have to break our heads as much as is necessary today, and yet we should be sure of accomplishing everything the given facts allow.

10. Indeed for a long time excellent men have brought to light a kind of "universal language" or "characteristic" in which diverse concepts and things were to be brought together in an appropriate order, with its help, it was to become for people of different nations to communicate their thoughts to one and to translate into their own language the written signs of a foreign language. However, nobody, so far, has gotten hold of a language which would embrace both the technique of discovering propositions and their critical examination -- a language whose signs or characters would play the same rôle as the signs of arithmetic for numbers and those of algebra for quantities in general. And yet it is as if God, when he bestowed these two sciences on mankind, wanted us to realize that our understanding conceals a far deeper secret foreshadowed by these two sciences.

11. Leibniz’s Calculating Machine:

12. George Boole on “The Laws of Thought” (1854): The design of the following treatise is to investigate the fundamental laws of those operations of the mind by which reasoning is performed; to give expression to them in the symbolic language of a Calculus, and upon this foundation to establish the science of Logic and construct its method.

13. They who are acquainted with the present state of the theory of Symbolic Algebra, are aware that the validity of the processes of analysis does not depend upon the interpretation of the symbols which are employed, but solely upon the laws of their combination. Every system of interpretation which does not affect the truth of the relations supposed, is equally admissible, and it is thus that the same processes may, under one scheme of interpretation, represent the solution of a question on the properties of number, under another, that of a geometrical problem, and under a third, that of a problem of dynamics or optics. ... It is upon the foundation of this general principle, that I purpose to establish the Calculus of Logic ... (Boole, 1845)

14. Boole on the “laws of thought”: Logic is essentially mathematics with just two values, 0 and 1. The basic logical connections are AND, OR, and NOT. AND yields a 1 only if both inputs are 1: 0 x 0 = 0 1 x 0 = 0 0 x 1 = 0 1 x 1 = 1 OR yields a 1 if at least one input is 1: 0 + 0 + 0 1 + 0 = 1 0 + 1 = 1 1 + 1 = 1 NOT yields the negation of whatever is put in: These correspond to the “logic gates” of a computer.

15. Alan Turing (1912-1954) “On Computable Numbers, with an Application to the Entscheidungsproblem” (1936) “Proposed Electronic Calculator” (1946) “Intelligent Machinery” (1948) “Computing Machines and Intelligence” (1950)

16. I propose to consider the question, “Can machines think?” This should begin with definitions of the meaning of the terms “machine” and “think”. The definitions might be framed so as to reflect so far as possible the normal use of the words, but this attitude is dangerous. If the meaning of the words “machine” and “think” are to be found by examining how they are commonly used it is difficult to escape the conclusion that the meaning and the answer to the question, “Can machines think?” is to be sought in a statistical survey such as a Gallup poll. Instead of attempting such a definition I shall replace the question by another, which is closely related to it and is expressed in relatively unambiguous words. Turing, “Computing Machines and Intelligence” (1950) (Available for download at www.jstor.org)

17. The “imitation game”: A = a man B = a woman C = an interrogator, who knows A and B only as X and Y, and who gets to ask questions of A and B.. C’s object is to determine which is which: either X is A and Y is B, or vice-versa. A’s object is to make C misidentify A and B. B’s object is to make C identify A and B correctly.

18. Turing’s new question: “What will happen when a machine takes the part of A in this game? Will the interrogator decide wrongly as often when the game is played like this as he does when the game is played between a man and a woman? These questions replace our original, “Can machines think?” “We are not asking whether all digital computers would do well in the game nor whether the computers at present available would do well, but whether there are imaginable computers which would do well.”

19. Basic elements of a computer: “Store”: a store of information, e.g. the human computer’s memory or calculations on paper. “Executive unit”: that which carries out the operations in a calculation “Control”: that which constrains the computer to carry out the instructions exactly. “Discrete state machine”: A machine that can be in a finite number of definitely distinct states, eg. “On” or “Off,” “Open” or “Closed”. A simple Turing machine: A device capable of reading, printing, and erasing symbols at defined places on a strip of paper or tape.

20. This special property of digital computers, that they can mimic any discrete state machine, is described by saying that they are universal machines. The existence of machines with this property has the important consequence that, considerations of speed apart, it is unnecessary to design new machines to do various computing processed. They can all be done with one digital computer, suitably programmed for each case. It will be seen that as a consequence of this all digital computers are in a sense equivalent. (Turing, 1950)

21. Objections to Turing’s account The Theological Objection: Thinking is a function of man’s immortal soul, so machines could never think. Reply: If theological arguments are allowed, it must be argued that God could not give a soul to an unthinking thing, or that he could not give our soul the same machinery for thinking that a computer uses. But there is no such argument. In any case, theological arguments have generally hindered science.

22. The “Head in the Sand” Objection: “The consequences of machines thinking would be too dreadful. Let us hope and believe that they cannot do so.” Reply: This is a feeling rather than a substantial argument requiring refutation.

23. The Mathematical Objection: There are non-computable functions, and therefore there are limits to the powers of discrete-state machines. Reply: It is not proven that humans are capable of computing the non-computable functions, either.

24. The Consciousness Objection: A machine can never have consciousness, which is a feature of human thought. Reply: We don’t know that other people think, since we can’t feel what their consciousness is like. We only think that they think because they pass the Turing test.

25. The Disability Argument: There are too many things that human thought can do that machines can’t do (e.g. self-reflection, appreciation of humor, etc.) Reply: We are not fully aware of the capacities of machines or people. It is not hard to foresee machines that are aware of their own states.

26. The Originality Objection: Machines don’t have the capacity to originate anything, or to do anything other than what they are told. Reply: It is foreseeable that there will be computers capable of learning. Moreover, it is not clear how original humans are, since human creativity is always manipulation of available ideas or images

27. The Continuity Objection: The human nervous system is continuous, unlike a digital computer. Reply: Digital computers can closely match the behaviour of continuous machines (e.g. in calculating irrational numbers).

28. The Informality Objection: Human behavior is informal, not subject to general rules like the behavior of a computer. Reply: Human behaviour is more subject to laws than we realize.