"I do not know what I may appear to the world,
but to myself I seem to have been only like a boy playing on the sea-shore,
and diverting myself in now and then
finding a smoother pebble or a prettier shell than ordinary,
whilst the great ocean of truth lay all undiscovered before me."
"A share in two revolutions
is living to some purpose."
Isaac Newton poetically and (perhaps faux-)modestly claims his life's work to have been the uneducated stumbling of a young hobbyist, untroubled by the vast unknown right beside him. He lived from 1642 to 1727, and wikipedia lists him as being a physicist, mathematician, astronomer, natural philosopher, alchemist and theologian. He is commonly called either the last of the alchemists or the first scientist, or something along these lines ("Newton was not the first of the Age of Reason: He was the last of the magicians." -John Maynard Keynes). His most famous work (which he wrote entirely in Latin, just to be difficult) the Principia (or Philosophiae Naturalis Principia Mathematica) gave us the laws of gravitation and motion, proved the solar-centric view of the solar system, and basically gave us all of macro physics. His classical mechanics was basically all of physics for three hundred years, until Einstein gave us relativity and quantum mechanics.
He built telescopes, studied sound and acoustics, light spectrums, heat and cooling, apocryphally invented the cat flap, gave us a whole bunch of mathematical functions I don't understand (calculus, binomial theorem, blah). It also turns out (years after his death Keynes acquired Newton's private papers on the subject of alchemy) that science, or natural philosophy, was just a hobby for wee Newt'. His most prolific writings were on religion, alchemy and magic – all of which, as a man of his time, he took seriously. That said his most massive contribution to us all will always be his Principia. There is no possible way I can portray the importance or magnitude of this work. Largely because I feel I am probably entirely unaware of the scale. As big as I think it is, as a scientific and mathematical illiterate, I cannot fully understand the achievement. I also don't read Latin...
What I can see is that his Rules of Reasoning in Philosophy appear to be the birth of the Scientific Method, possibly the greatest ever human construction. Scientific Method has given us everything – everything. It is the reason death during childbirth is rare, the reason we live to be 90, the reason we go on holiday, the reason we go to work, the reason we don't toil and die on the land. And it began thusly in 1726:
Rule 1: We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances.
Rule 2: Therefore to the same natural effects we must, as far as possible, assign the same causes.
Rule 3: The qualities of bodies, which admit neither intensification nor remission of degrees, and which are found to belong to all bodies within the reach of our experiments, are to be esteemed the universal qualities of all bodies whatsoever.
Rule 4: In experimental philosophy we are to look upon propositions inferred by general induction from phenomena as accurately or very nearly true, not withstanding any contrary hypothesis that may be imagined, till such time as other phenomena occur, by which they may either be made more accurate, or liable to exceptions.
Scientific Method is the difference between belief in evidence (i.e. truth) and belief in faith (i.e. fantasy). It is often simplified to:
Define a question. Gather information and resources (observe). Form an explanatory hypothesis. Perform an experiment and collect data, testing the hypothesis. Analyze the dataInterpret the data and draw conclusions that serve as a starting point for new hypothesis. Publish results. Retest (frequently done by other scientists).
We hold these truths to be self evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.