The English physicist and mathematician Sir Isaac Newton was one of the leading figures in the scientific revolution of 17th century England. In optics, his discovery of the composition of white light integrated the phenomena of colours into the science of light and laid the foundation for modern physical optics. In mechanics, his three laws of motion, the basic principles of modern physics, resulted in the formulation of the law of universal gravitation. In mathematics, he was the original discoverer of the infinitesimal calculus. Newton's Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), 1687, was one of the most important single works in the history of modern science. Formative influences

Born in Woolsthorpe, Sir Isaac Newton was the only son of a local farmer, who was also called Isaac Newton. He died three months before Isaac Jnr was born. The same year, at Arcetri, Galileo Galilei also died; Newton would eventually pick up his idea of a mathematical science of motion. he would bring Galileo's work to completion.

A small, sickly baby, Isaac Newton wasn't expected to survive his first few days, much less the 84 years he eventually lived. Deprived of pater before birth, he soon lost mater, for two years later she married for a second time; her second husband, the well off minister Barnabas Smith, left young Newton with his grandmother and moved to a neighbouring village to raise a son and two daughters. For nine years, until the death of Barnabas Smith in 1653, Isaac was effectively separated from mater. Newton's well known psychotic tendencies have been ascribed to this traumatic period.

The fact Newton hated his stepfather we can be certain. When he examined the state of his soul in 1662 and compiled a catalog of sins in shorthand, he remembered "Threatning my father and mother Smith to burne them and the house over them." The acute sense of insecurity that rendered him obsessively anxious when his work was published and irrationally violent when he defended it accompanied Newton throughout his life and can plausibly be traced to his early years.

After his mother was widowed a second time, she determined that her first-born son should manage her now considerable property. It quickly became apparent, however, that this would be a disaster, both for the estate and for Newton. He could not bring himself to concentrate on rural affairs--set to watch the cattle, he would curl up under a tree with a book. Fortunately, the mistake was recognized, and Newton was sent back to the grammar school in Grantham, where he had already studied, to prepare for the university. As with many of the leading scientists of the age, he left behind in Grantham anecdotes about his mechanical ability and his skill in building models of machines, such as clocks and windmills. At the school he apparently gained a firm command of Latin but probably received no more than a smattering of arithmetic. By June 1661, he was ready to matriculate at Trinity College, somewhat older than the other undergraduates because of his interrupted education.

When Newton arrived in Cambridge in 1661, the movement now known as the scientific revolution was well underway, and many of the works basic to modern science had already appeared. Astronomers like Copernicus had advanced the heliocentric system of the solar system. Galileo proposed the foundations of a new mechanics built on the fundamentals of inertia. Led by Descartes, philosophers had begun to formulate a new conception of nature as an intricate, and inert machine. Yet as far as the universities of Europe, including Cambridge, were concerned, all this might well have never happened. They continued to be the strongholds of outmoded Aristotelianism, which rested on a geocentric view of the universe, which dealt with nature in qualitative rather than quantitative terms.

Like thousands of other new interns, Newton began his higher education by immersing himself in Aristotle's work. Even though the new philosophy was not in the curriculum, it was in the air. Some time during his early career, Isaac Newton stumbled across the works of the French natural philosopher René Descartes and the other mechanical philosophers, who, in contrast to Aristotle, viewed physical reality as composed entirely of particles of matter in motion and who held that all the reason of nature result from mechanical interaction. A new set of notes, which he entitled "Quaestiones Quaedam Philosophicae" Certain Philosophical Questions, begun sometime in 1664, usurped the unused pages of a notebook intended for traditional scholastic exercises; under the title he entered the slogan "Amicus Plato amicus Aristoteles magis amica veritas" Plato is my friend, Aristotle is my friend, but my best friend is the truth. Isaac Newton's scientific career was underway.

The "Quaestiones" reveal that he had discovered the new conception of nature which provided the pivotal framework of the scientific revolution. Newton carefully mastered the works of Descartes and had also discovered that the French philosopher Pierre Gassendi had revived atomism, an alternative mechanical system to explain nature. The "Quaestiones" also reveal that Newton already was inclined to find the latter a more attractive philosophy than Cartesian natural philosophy, which rejected the existence of ultimate indivisible particles. The works of the 17th-century chemist Robert Boyle provided the foundation for Newton's considerable work in chemistry. Significantly, he had read Henry More, the Cambridge Platonist, and was thereby introduced to another intellectual world, the magical Hermetic tradition, which sought to explain natural phenomena in terms of alchemical and magical concepts. The two traditions of natural philosophy, the mechanical and the Hermetic, antithetical though they appear, continued to influence his thought and in their tension supplied the fundamental theme of his scientific career.