The Life Of...

Robert Boyle (1627-1691)

Robert Boyle was born at Lismore Castle, Munster on 25 January 1627, the fourteenth child and seventh son of Richard Boyle, 1st Earl of Cork. Robert Boyle was educated mainly by tutors and himself. He had no formal university education but read widely and made contact with many of the most important natural philosophers of his day, both at home and abroad. He had independent means which enabled him to have his own laboratory and to support religious charities. He was active in the 'Invisible College', an informal body devoted to the 'new philosophy' which in 1663 became the Royal Society, of which he was a Council member. He moved to Oxford in 1654, where he set up a laboratory with Robert Hooke as his assistant There he did most of his experimental work until 1668 when he went to live in London with his sister Lady Ranelagh.

He was made an honorary Doctor of Medicine of Oxford in 1688. In his autobiographical account (Works, vol. 1, pp. xxi-xxvi) he reflects on his noble birth that 'being born heir to a great family is but a glittering kind of slavery' and 'is ever an impediment to the knowledge of many retired truths, that cannot be attained without familiarity with meaner persons'. He indeed developed a keen interest in the work of artisans because they tend to know more than anyone else about the materials of their trades. He makes a general remark about religious beliefs that 'though we cannot always give a reason for what we believe, we should ever be able to give a reason why we believe it', which is surely a precept that guided his attitude to natural philosophy as well.

Boyle was a prolific writer and experimenter on most scientific subjects that were attracting interest at the time. He investigated some alchemical claims about which he was largely skeptical in his published works. He was a devoutly religious man but wrote mainly about practical and ethical religious matters rather than engaging in theological controversy. He argued for the tolerance of different religious beliefs, and spent a good deal of money on propagating the gospel in New England and the Orient, sponsoring translations of the Bible into foreign languages.

He published many experimental reports and did original work on chemical indicators, human blood, color, fire, medicine, and hydrostatics. With Hooke he developed Guericke's air pump, which he needed for his experiments. His first major publication was his book on the 'spring' of the air (1660), in the second edition of which (1662) we find the first statement of what came to be known as 'Boyle's Law', about the relation between the pressure and volume of gases (Works, vol. 1, pp. 156-9). He expressed admiration for Bacon's Novum Organum, Descartes's Principles of Philosophy, and the work of ancient and recent atomists, although he says that in his early days he refrained from reading them carefully because he feared that he might be seduced by their reliance on pure reason rather than observation and experiment. He hoped to provide empirical evidence relevant to their views.

Perhaps Boyle's most interesting and influential contribution was his 'corpuscular or mechanical hypothesis', probably the fullest and most detailed development of physical atomism up to his time. His work on this begins in earnest in The Sceptical Chymist (1661) but it receives its clearest exposition in The Origin of Forms and Qualities (1666), and he returns to it in many of his later works. A useful summary of its basic principles is to be found in his About the Excellency and Grounds of the Mechanical Philosophy (1674).

Boyle leads up to his hypothesis by considering in detail and attacking the forms of explanation and their basic concepts that he found natural philosophers using in the sixteenth and early seventeenth centuries. They fall into two main classes which sometimes overlap: those favored by the 'chymists' or 'spagyrists', and those favored by the 'Aristotelians' or 'peripatetics'. The chymists' explanations were based on the tria prima, the three chemical 'principles' salt, sulfur, and mercury which they regarded as ingredients of all substances. These explanations depended on the presence in observable bodies and materials of various proportions of the principles. They were not identical with the chemical substances of the same names but were kinds of essences of them.

Observable objects, according to the hypothesis, are composed of innumerable solid corpuscles separated by empty space which allows the physical divisibility of the objects, their expansion and contraction, and changes of shape. Chemical reactions may be explained by changes of texture involving the inter-penetration of groups of corpuscles and the entrapment or release of individual corpuscles by groups of them. The hypothesis is highly versatile just because the corpuscles are composed of one universal matter and so have few qualities.

Although Boyle has strong empiricist leanings, unobservable corpuscles hold no terrors for him because they are described in terms of kinds of qualities that are met within experience on the large scale and because he has the conception of a hypothetico-deductive method. The test of the worth of the hypothesis will be empirical and will depend upon the comparison of its deduced consequences in specific circumstances with the results of experiment; that is, on the adequacy of its explanations and the success of its predictions. If the hypothesis is contradicted by observed evidence,