demonstrated, the Chinese tried.50 It is true that glass, although known in China, was not in wide use, in part perhaps the result of supply considerations (expensive fuel), and possibly in part due to lack of demand (tea was drunk in porcelain cups, and the Chinese examined themselves in polished bronze mirrors).51 Some past societies might well have made lenses given enough time and better luck: Islamic civilization for centuries had a magnificent glass industry, yet never came up withe either spectacles or a telescope, despite the ubiquity of presbyopia and a strong interest in astronomy. In the later Middle Ages, glass making in the Islamic world declined, in part because of the devastation inflicted by the Mongols.
But elsewhere knowledge must have played a central role. Tokugawa Japan had a flourishing industry making glass trinkets and ornaments, but no optical instruments emerged there either until the Meiji restoration. Not having access to the Hellenistic geometry that served not only Ptolemy and Alhazen, but also sixteenth century Italians such as Francesco Maurolico (1494-1575) who studied the characteristics of lenses, made the development of optics in the Orient difficult. The probability of a microscope being invented by someone who does not have access to geometry is very low, although it cannot be ruled out that a different kind of mathematics, not imagined by us, could have achieved the same results. Had China been the world, or had the West never had “western” science, optical devices similar to the ones we have would in all likelihood never have been developed.52 One might then seriously wonder whether bacteriology and metallography, which both depended on microscopes, would ever have emerged.
The complexity of the question of the critical role of useful knowledge is demonstrated by a later invention, anaesthetics. Much like eyeglasses, the “demand” or necessity for anesthetics were hardly time- or society-specific, although the willingness and ability to tolerate and inflict pain are of course to some extent culturally determined. For hundreds of years Europeans suffered unspeakably from operations carried out without anesthesia. The discovery that a number of substances could knock a patient unconscious without long-term damage must have increased total consumer surplus (if not
50Thus in the Hua Shu (Book of Transformations) dated to the middle of the tenth century there is clear-cut reference to four types of lenses that enlarge, reduce, upright and invert. The author points out that when he looks at people he realized that there was no such thing as largeness or smallness, beauty or ugliness. (Needham, Science and Civilization: Physics , p. 117).
51On this, see Alan MacFarlane and Gerry Martin, The Glass Effect: Glass and World History, 2002.
52It is telling that when Western applied optics arrived in China through Jesuit travelers in the seventeenth century, Chinese artisans such as Po Yü and Sun Yün-Chhiu soon constructed microscopes, searchlights, and magnifying glasses. Needham himself concedes that the view that regarded spectacles to have been a Chinese invention is a myth. Subsequent to their invention in the West, they found their way to China rather quickly. One must conclude that the Chinese were not indifferent to applied optics, but simply were unable to create the techniques. Colin Ronan and Joseph Needham, The Shorter Science and Civilization in China, Vol. I, 1978, p. 257. Needham, Science and Civilization: Physics, pp. 118-19.