Andrew Janiak on Isaac Newton, Philosopher

To understand Newton's genius, Duke professor recreates the intellectual world of 1700

A Newtonian reflecting telescope, one of his many inventions that changed our understanding of the world. Photo: Andrew Dunn/Wikimedia Commons
A Newtonian reflecting telescope, one of his many inventions that changed our understanding of the world. Photo: Andrew Dunn/Wikimedia Commons

The argument that Isaac Newton was the greatest scientist ever gets a lot of support these days, but there’s one important person who might disagree: Newton himself.

In his new book "Newton," Duke philosophy professor Andrew Janiak makes the case for considering Newton as Newton himself did – a "natural philosopher." This isn't just a quirk of language; Janiak says it's essential to understanding his remarkable achievements.

Born on Christmas Day in 1642, Newton benefited from what we call the Scientific Revolution, but Janiak writes that the word "scientist" didn't come into use until more than two centuries later. There was no consensus on issues such as the value of math or experimental results in describing the world. The great thinkers of the time closely tied their study of the world with philosophical discussions of the nature of matter and their belief in God.

The one consensus of the great thinkers of the time was that the world ran on mechanistic principles and that the role of the scholar was to describe the method of the workings of the world, much in the way they would describe the workings of a clock. Descartes, for example, believed planets moved around the sun because of a vortex in which particles carried the planets in their orbit.

Janiak said Newton's genius was to ignore all this. His major work, "Mathematical Principles of Natural Philosophy" – frequently referred to as "Principia" – represents a break from the beliefs of the time and constitutes Newton's defense against criticisms from leading philosophers of the day, particularly Gottfried Leibniz and his followers.

Isaac Newton

Portrait of Isaac Newton, around 1715. Photo: English School via Wikimedia Commons

Below, Janiak discusses his book in a conversation with Geoffrey Mock of Duke Today.

Q: Why is it important to understand Newton in his own terms rather than how his work is relevant to us?

Janiak: It's not different from thinking about any historical event, such as the Civil War. We can approach the Civil War by asking what the lasting implications are for us. But that's a different question than trying to figure out what was the Civil War meant to those involved? To answer that question, you can't adopt a contemporary point of view.

There are hundreds of books written about what Newton's ideas mean for us.  I figured I didn't need to write that account. What is less well known was how he was viewed during his own lifetime. What was his life like and how was his work treated by the other great thinkers of his time? What we forget was that he didn't know for certain whether he was on the right track. The number one lesson I took away from this is that in 1700, at the peak of Newton's powers, nobody was certain that he was right. We know things now that they didn't know then.

When "Principia" came out it was evident this was an important book. All the great thinkers either supported him or felt like they had to respond to him in criticism. Leibniz knew he had to respond to Newton.  Leibniz clearly was an important figure, a brilliant man, co-founder with Newton of the calculus. Newton himself was interested in what Leibniz was doing. But Leibniz was deeply opposed to what Newton was doing.  Part of my effort was to reconstruct why it was rational at the time for someone like Leibniz to oppose Newton.


Q: You remind us that methods we take for granted in science weren't widely accepted at the time.

Andrew Janiak
Andrew Janiak. Photo: Duke Photography

Janiak: It's important not to take certain things for granted.  If things like the value of observation and experiment are important in modern science, it's because Newton and others debated these things. It took many, many years to settle those debates. 

Leibniz didn't just criticize Newton's theories. His criticism was about Newton's entire approach. Leibniz's claim was this: if all the great thinkers of the time knew anything at all it was that they needed a mechanistic explanation of how the natural world works. And now Newton comes along and says no explanation is needed, all we need is to understand the math and to postulate forces like gravity.

Leibniz and many others were incredulous. Leibniz said that after more than a century of the scientific revolution—although nobody called it that then—how can we end up with one thing that everyone agrees on, viz., a mechanistic approach to nature, and suddenly Newton says that we have to give that up? This is a testament to just what a genius Newton really was, because he saw what other great thinkers of his time—people he studied and admired like Boyle and Descartes and Leibniz—couldn't see. To say the things that he said took real courage. 

But it also explains why people rationally opposed him.  They truly thought that if you give up the mechanistic philosophy, you might as well give up all the intellectual progress that had occurred and go back to the days of Aristotle.


Q: How was Newton a transitional figure in science and philosophy?

Janiak: In the wake of what he did, not what he did himself, but in the aftermath, we get specialization. By 1800, roughly, you can begin to see the modern disciplines of biology, chemistry and physics.  Philosophy goes in another direction.  It's interesting to think of this in biological terms. Natural philosophy goes extinct, but it evolves and branches out. One branch becomes science, and the other becomes philosophy.

By his methods and approaches, his emphasis on math and experiment, Newton is important in making that change happen. But the real danger is in thinking it happened during his own lifetime. In fact, it came generations later.


Q: It's also surprising to find that Principia is filled with discussions of the nature of God. It's a reminder that Newton had other interests in things that aren't part of modern science, such as alchemy, Biblical codes and prophesy.

Janiak: Alchemy conjures up images of taking elements and turning it into gold, but in fact what Newton was doing was a lot of experiments. He wrote very extensively about these experiments but didn't publish most of it.  We can understand it as an early form of chemistry.

But he also was writing about Biblical interpretation and codes and timetables.  It's something people don't talk much about now, but it's strange only if we think of him as a modern scientist. If you do that, all this kind of work becomes totally foreign. How could a scientist be interested in predicting the date of the end of the world? Newton was. This is one way in which to call him a scientist is historically inaccurate. The world that he lived in was fundamentally different from our world.

We must remember that point, despite the fact that he did as much as anyone in modern history to create the world that we live in.