Leibniz's first great mathematical success was his creation of a calculating machine in the early 1670's. It was apparently the first machine capable of multiplication, division, and root extractions, and was impressive enough to get Leibniz elected to the Royal Society of London in 1673. He later (in a 1685 manuscript) gave the following account of the moment of inspiration for this invention: 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. The calculating box of Pascal was not known to me at that time... When I noticed, however, the mere name of a calculating machine in the preface of his "posthumous thoughts"...I immediately inquired about it in a letter to a Parisian friend. When I learned from him that such a machine exists I requested the most distinguished Carcavius by letter to give me an explanation of the work which it is capable of performing. This pattern of discovery seems to have been charactistic of Leibniz. He was a sponge for knowledge and ideas, and he was tireless in ferreting it out of friends, acquaintences, and strangers alike. He tells us that, once he had gotten all the information he could about Pascal's machine, he set himself the task of making an even better machine. However, notice that he begins the discussion by recalling the earlier moment of inspiration when he saw the step- counting machine, and how "it occurred to me AT ONCE that the entire arithmetic could be subjected to a similar kind of machinery". In other words, this was the moment when his invention of the calculating machine actually occurred, although he didn't act on the inspiration at the time. It was only later, when he saw the words "calculating machine" in some papers of Pascal, that he was prompted to actually design such a machine - after studying the design and capabilities of Pascal's machine. There are some interesting parallels between this sequence of events and Leibniz's development of the calculus. In January of 1673, soon after taking up the serious study of mathematics (enlisting Christian Huygens as a tutor!), he visited London and made the acquaintance of Heinrich (Henry) Oldenberg, the secretary of the Royal Society of London. In April of that year Leibniz received from Oldenberg a report drawn up by John Collins on the state of mathematics in England. A prominent part of this report was a list of problems (many involving infinite series) that could be solved by an unspecified method possessed by a secretive man at Cambridge named Isaac Newton. As Leibniz later remembered it, he himself had already had the original inspiration for calculus, prior to seeing any of the reports on the work of Barrow, Gregory, and Newton, and there was no actual description of calculus in the 1673 report, but it's possible to imagine that, as with the appearance of the "mere name" of a calculating machine in Pascal's papers, the mere mention of a wonderful general method for handling a wide range of mathematical problems of this kind was enough to perk up Leibniz's ears and set him working in ernest on the task of developing his own ideas for the calculus. By 1675 (or so) he had a method that was, for practical purposes, at least the equal of Newton's fluxions (which Newton, builing on the work of Isaac Barrow, had developed in the mid-1660's), although his philosophical justification for it was perhaps less sophisticated than Newton's. In that year, and on into 1676, there was an exchange of letters between Newton and Leibniz (via Oldenberg) in which Newton, although still very reticent about revealing general methods, gave even more explicit hints of calculus, including even an anagram stating the inverse relationship between differentiation and integration. At this point it's clear that Leibniz was already in possession of his own version of calculus. Thus the two men, each having made the same great discovery, neither having published on the subject, were corresponding with each other, and we can imagine that they were each trying to figure out exactly how much the other knew, without revealing too much of what he himself knew. These letters became infamous during the subsequent priority dispute, but (in my opinion) it was the Collins report of 1673 that (analagous to the mere mention of the words "calculating machine") represents the crucial influence of the British mathematicians on Leibniz's discovery of calculus. In any case, Leibniz was certainly an enormously creative and brilliant man, and his roles in the development of both the calculus and the artificial computer were tremendously beneficial. Toward the end of his 1685 computer manuscript, with the characteristically Leibnizian title "Machina arithmetica in qua non additio tantum et subtractio sed et multiplicatio nullo, divisio vero paene nullo animi labore peragantur" he wrote about the value of the computer: "...the astronomers surely will not have to continue to exercise the patience which is required for computation. It is this that deters them from computing or correcting tables, from the construction of Ephemerides, from working on hypotheses, and from discussions of observations with each other. For it is unworthy of excellent men to lose hours like slaves in the labour of calculation which could safely be relegated to anyone else if machines were used." It's interesting that one of the persistent themes in all of Leibniz's work was the idea of reducing thought processes to automatic and/or mechanical operations that could "safely be relegated to anyone". This was true not only in his development of the computer, but also in his reduction of calculus to a set of straightforward algorithms on a well-defined set of symbols. Likewise his work on the "universal characteristic", which we would now call symbolic logic, was intended to reduce all thought to a set of definite rules, or, as he wrote, "...a general method in which all truths of reason would be reduced to a kind of calculation. At the same time, this would be a sort of universal language or script, but infinitely different from all those imagined previously, because its symbols and words would direct the reason, and errors - except those of fact - would be mere mistakes in calculation..." Leibniz was, after all, originally trained as a lawyer, so it may be understandable that he yearned for some automatic way of settling disputes. The youthful optimism of Leibniz in this regard was later satirized by Voltaire in the play Candide ("Come, let us calculate"). On the other hand, is it too farfetched to see in Leibniz's view that we inhabit the "best of all possible worlds" some hint of Maupertius' principle of least action?

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