For Isaac Newton (1642-1727), the universe was governed by precise laws which could not only be formulated but mathematically proved to a certainty. These physical laws were not sporadic or local; they were universal and extended “everywhere to immense distances,” as he wrote in “The Principia: Mathematical Principles of Natural Philosophy,” first published in 1687. Newton’s three laws of motion may not apply at the atomic level or under conditions approaching the speed of light, as we now know, but they apply everywhere else. The fall of that famous apple was no less an effect of universal gravitation than the rhythms of the tides or the orbits of the planets.

But to prove the law of gravity, though an unparalleled accomplishment, was not to understand its final cause. Newton wrote, again in “The Principia,” that “I have not as yet been able to deduce from phenomena the reason for these properties of gravity.” (That “as yet” demonstrates both Newton’s supreme self-confidence and his rigorous honesty. To this day no one else has deduced those “properties” either.) In a statement that stands as his scientific signature, he added, “et non fingo hypotheses” — “and I do not feign hypotheses.” Even so, this same scorner of the hypothetical would spend much of his career after the amazing two-year period of his greatest discoveries in 1664-66 dabbling obsessively in alchemy, as well as pursuing increasingly fantastic numerological investigations of Scripture.

This side of Newton’s character has at times puzzled and embarrassed his admirers. But as Peter Ackroyd shows in his astute, and beautifully written, “Newton” (Doubleday, 177 pages, $21.95), the quest for order was from the beginning as much spiritual — and indeed, fervently religious — as it was scientific. According to Mr. Ackroyd, Newton believed that his destiny lay “in the discovery and interpretation of the works of God.” To seek the transmutation of matter through alchemy or to devise intricate chronologies of the future on the basis of the Bible was also to search for “the secret of the universe.” As Mr. Ackroyd notes, it was the same driving impulse that led to “The Principia.”

Not surprisingly, the prolific Mr. Ackroyd, who is the author of 12 novels as well as biographies of Dickens, Thomas More, and Shakespeare — not to mention at least four histories of London — excels at re-creating the look and feel, at once grubby and exalted, of Newton’s milieu. And Newton the man comes through splendidly in all the sheer arrogance of his driven genius. To critics and rivals, such as Robert Hooke, he could be witheringly dismissive. To those he considered his inferiors — virtually everyone — he was often petty and vindictive; he even squabbled rather childishly with Leibniz over the credit for the invention of calculus (both seem to have hit upon it independently). He hounded John Flamsteed, the Royal Astronomer, for years and eventually confiscated Flamsteed’s star catalog, the astronomer’s life work, for his own purposes. He ruled the Royal Society, of which he became president in 1703, with despotic efficiency, making of it, in Mr. Ackroyd’s words, “a kind of court with its own sovereign.” At the same time, Newton transformed the society, turning it into the leading scientific organization of the age. And he could be tender. When his mother lay dying, he nursed her night and day for weeks and, according to a witness, “dressed all her blisters with his own hands.”

This is the third in a series of “Ackroyd’s Brief Lives” (the first two dealt with Chaucer and Turner) and though admirable on Newton’s life, the book is, perhaps inevitably, less satisfactory on his scientific achievements. Mr. Ackroyd does give a good account of Newton’s discoveries in optics. Newton set a prism in front of a peephole in a darkened room and the entering light was refracted against a wall 22 feet away to display the array of the spectrum; by such experiments he succeeded in proving that so-called white light was in fact heterogeneous, a composite of all the colors of light. This was not just, as Newton first said, “a very pleasing divertisement,” but provided a fundamental insight into the nature of light itself. He also documents Newton’s considerable “mechanical ingenuity” from an early age. He built an exceptionally accurate clock and a superb reflecting telescope — now known as the “Newtonian telescope” — and he constructed them both entirely by hand (the telescope was later presented to a delighted King Charles II). But his account of “The Principia” is cursory at best. Mr. Ackroyd’s treatment of this colossal work, which Newton wrote in an astonishing 18 months — and which the great astronomer Edmond Halley, an admirer, saw through the press — gives little sense of its riches.

By the oddest of misjudgments, Newton came to be seen by some as a dismantler of the divine in favor of a merely mechanical universe. In a letter, the poet William Blake wrote, “Pray God us keep / From Single vision & Newton’s sleep!” and in a poem, he famously mocked “Newton’s particles of light.” Blake didn’t know how right he was. Newton’s vision was single: Even gravity was based “only in the arbitrary will of God.” In his epitaph for Newton, Alexander Pope expressed it best:

Nature, and Nature’s laws lay hid in Night.

God said, “Let Newton be!” And all was Light.

eormsby@nysun.com